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commit cf8aa9bf97cadf85745506c6a3e244b22c268d63 upstream.
The "buf" flexible array needs to be the memcpy() destination to avoid
false positive run-time warning from the recent FORTIFY_SOURCE
hardening:
memcpy: detected field-spanning write (size 93) of single field "&fh->fb"
at fs/overlayfs/export.c:799 (size 21)
Reported-by: syzbot+9d14351a171d0d1c7955@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/000000000000763a6c05e95a5985@google.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 4f11ada10d0ad3fd53e2bd67806351de63a4f9c3 upstream.
If st_uid/st_gid doesn't have a mapping in the mounter's user_ns, then
copy-up should fail, just like it would fail if the mounter task was doing
the copy using "cp -a".
There's a corner case where the "cp -a" would succeed but copy up fail: if
there's a mapping of the invalid uid/gid (65534 by default) in the user
namespace. This is because stat(2) will return this value if the mapping
doesn't exist in the current user_ns and "cp -a" will in turn be able to
create a file with this uid/gid.
This behavior would be inconsistent with POSIX ACL's, which return -1 for
invalid uid/gid which result in a failed copy.
For consistency and simplicity fail the copy of the st_uid/st_gid are
invalid.
Fixes: 459c7c565ac3 ("ovl: unprivieged mounts")
Cc: <stable@vger.kernel.org> # v5.11
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Seth Forshee <sforshee@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit baabaa505563362b71f2637aedd7b807d270656c upstream.
Missed an error cleanup.
Reported-by: syzbot+fd749a7ea127a84e0ffd@syzkaller.appspotmail.com
Fixes: 2b1a77461f16 ("ovl: use vfs_tmpfile_open() helper")
Cc: <stable@vger.kernel.org> # v6.1
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 456b59e757b0c558df550764a4fd5ae6877e93f8 upstream.
ovl_change_flags() is an open-coded variant of fs/fcntl.c:setfl() and it
got missed by commit 164f4064ca81 ("keep iocb_flags() result cached in
struct file"); the same change applies there.
Reported-by: Pierre Labastie <pierre.labastie@neuf.fr>
Fixes: 164f4064ca81 ("keep iocb_flags() result cached in struct file")
Cc: <stable@vger.kernel.org> # v6.0
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216738
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 5b0db51215e895a361bc63132caa7cca36a53d6a upstream.
There is a wrong case of link() on overlay:
$ mkdir /lower /fuse /merge
$ mount -t fuse /fuse
$ mkdir /fuse/upper /fuse/work
$ mount -t overlay /merge -o lowerdir=/lower,upperdir=/fuse/upper,\
workdir=work
$ touch /merge/file
$ chown bin.bin /merge/file // the file's caller becomes "bin"
$ ln /merge/file /merge/lnkfile
Then we will get an error(EACCES) because fuse daemon checks the link()'s
caller is "bin", it denied this request.
In the changing history of ovl_link(), there are two key commits:
The first is commit bb0d2b8ad296 ("ovl: fix sgid on directory") which
overrides the cred's fsuid/fsgid using the new inode. The new inode's
owner is initialized by inode_init_owner(), and inode->fsuid is
assigned to the current user. So the override fsuid becomes the
current user. We know link() is actually modifying the directory, so
the caller must have the MAY_WRITE permission on the directory. The
current caller may should have this permission. This is acceptable
to use the caller's fsuid.
The second is commit 51f7e52dc943 ("ovl: share inode for hard link")
which removed the inode creation in ovl_link(). This commit move
inode_init_owner() into ovl_create_object(), so the ovl_link() just
give the old inode to ovl_create_or_link(). Then the override fsuid
becomes the old inode's fsuid, neither the caller nor the overlay's
mounter! So this is incorrect.
Fix this bug by using ovl mounter's fsuid/fsgid to do underlying
fs's link().
Link: https://lore.kernel.org/all/20220817102952.xnvesg3a7rbv576x@wittgenstein/T
Link: https://lore.kernel.org/lkml/20220825130552.29587-1-zhangtianci.1997@bytedance.com/t
Signed-off-by: Zhang Tianci <zhangtianci.1997@bytedance.com>
Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Fixes: 51f7e52dc943 ("ovl: share inode for hard link")
Cc: <stable@vger.kernel.org> # v4.8
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 672e4268b2863d7e4978dfed29552b31c2f9bd4e upstream.
ovl_dentry_revalidate_common() can be called in rcu-walk mode. As document
said, "in rcu-walk mode, d_parent and d_inode should not be used without
care".
Check inode here to protect access under rcu-walk mode.
Fixes: bccece1ead36 ("ovl: allow remote upper")
Reported-and-tested-by: syzbot+a4055c78774bbf3498bb@syzkaller.appspotmail.com
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
Cc: <stable@vger.kernel.org> # v5.7
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 23a8ce16419a3066829ad4a8b7032a75817af65b ]
Underlying fs doesn't remove privs because fallocate is called with
privileged mounter credentials.
This fixes some failure in fstests generic/683..687.
Fixes: aab8848cee5e ("ovl: add ovl_fallocate()")
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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[ Upstream commit b306e90ffabdaa7e3b3350dbcd19b7663e71ab17 ]
Underlying fs doesn't remove privs because copy_range/remap_range are
called with privileged mounter credentials.
This fixes some failures in fstest generic/673.
Fixes: 8ede205541ff ("ovl: add reflink/copyfile/dedup support")
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs tmpfile updates from Al Viro:
"Miklos' ->tmpfile() signature change; pass an unopened struct file to
it, let it open the damn thing. Allows to add tmpfile support to FUSE"
* tag 'pull-tmpfile' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fuse: implement ->tmpfile()
vfs: open inside ->tmpfile()
vfs: move open right after ->tmpfile()
vfs: make vfs_tmpfile() static
ovl: use vfs_tmpfile_open() helper
cachefiles: use vfs_tmpfile_open() helper
cachefiles: only pass inode to *mark_inode_inuse() helpers
cachefiles: tmpfile error handling cleanup
hugetlbfs: cleanup mknod and tmpfile
vfs: add vfs_tmpfile_open() helper
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Pull vfs constification updates from Al Viro:
"whack-a-mole: constifying struct path *"
* tag 'pull-path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
ecryptfs: constify path
spufs: constify path
nd_jump_link(): constify path
audit_init_parent(): constify path
__io_setxattr(): constify path
do_proc_readlink(): constify path
overlayfs: constify path
fs/notify: constify path
may_linkat(): constify path
do_sys_name_to_handle(): constify path
->getprocattr(): attribute name is const char *, TYVM...
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Pull vfs file updates from Al Viro:
"struct file-related stuff"
* tag 'pull-file' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
dma_buf_getfile(): don't bother with ->f_flags reassignments
Change calling conventions for filldir_t
locks: fix TOCTOU race when granting write lease
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If tmpfile is used for copy up, then use this helper to create the tmpfile
and open it at the same time. This will later allow filesystems such as
fuse to do this operation atomically.
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Now that we don't perform translations directly in vfs_setxattr()
anymore we can constify the @value argument in vfs_setxattr(). This also
allows us to remove the hack to cast from a const in ovl_do_setxattr().
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org>
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The posix_acl_from_xattr() helper should mainly be used in
i_op->get_acl() handlers. It translates from the uapi struct into the
kernel internal POSIX ACL representation and doesn't care about mount
idmappings.
Use the vfs_set_acl_prepare() helper to generate a kernel internal POSIX
ACL representation in struct posix_acl format taking care to map from
the mount idmapping into the filesystem's idmapping.
The returned struct posix_acl is in the correct format to be cached by
the VFS or passed to the filesystem's i_op->set_acl() method to write to
the backing store.
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org>
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filldir_t instances (directory iterators callbacks) used to return 0 for
"OK, keep going" or -E... for "stop". Note that it's *NOT* how the
error values are reported - the rules for those are callback-dependent
and ->iterate{,_shared}() instances only care about zero vs. non-zero
(look at emit_dir() and friends).
So let's just return bool ("should we keep going?") - it's less confusing
that way. The choice between "true means keep going" and "true means
stop" is bikesheddable; we have two groups of callbacks -
do something for everything in directory, until we run into problem
and
find an entry in directory and do something to it.
The former tended to use 0/-E... conventions - -E<something> on failure.
The latter tended to use 0/1, 1 being "stop, we are done".
The callers treated anything non-zero as "stop", ignoring which
non-zero value did they get.
"true means stop" would be more natural for the second group; "true
means keep going" - for the first one. I tried both variants and
the things like
if allocation failed
something = -ENOMEM;
return true;
just looked unnatural and asking for trouble.
[folded suggestion from Matthew Wilcox <willy@infradead.org>]
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Ensure that POSIX ACLs checking, getting, and setting works correctly
for filesystems mountable with a filesystem idmapping ("fs_idmapping")
that want to support idmapped mounts ("mnt_idmapping").
Note that no filesystems mountable with an fs_idmapping do yet support
idmapped mounts. This is required infrastructure work to unblock this.
As we explained in detail in [1] the fs_idmapping is irrelevant for
getxattr() and setxattr() when mapping the ACL_{GROUP,USER} {g,u}ids
stored in the uapi struct posix_acl_xattr_entry in
posix_acl_fix_xattr_{from,to}_user().
But for acl_permission_check() and posix_acl_{g,s}etxattr_idmapped_mnt()
the fs_idmapping matters.
acl_permission_check():
During lookup POSIX ACLs are retrieved directly via i_op->get_acl() and
are returned via the kernel internal struct posix_acl which contains
e_{g,u}id members of type k{g,u}id_t that already take the
fs_idmapping into acccount.
For example, a POSIX ACL stored with u4 on the backing store is mapped
to k10000004 in the fs_idmapping. The mnt_idmapping remaps the POSIX ACL
to k20000004. In order to do that the fs_idmapping needs to be taken
into account but that doesn't happen yet (Again, this is a
counterfactual currently as fuse doesn't support idmapped mounts
currently. It's just used as a convenient example.):
fs_idmapping: u0:k10000000:r65536
mnt_idmapping: u0:v20000000:r65536
ACL_USER: k10000004
acl_permission_check()
-> check_acl()
-> get_acl()
-> i_op->get_acl() == fuse_get_acl()
-> posix_acl_from_xattr(u0:k10000000:r65536 /* fs_idmapping */, ...)
{
k10000004 = make_kuid(u0:k10000000:r65536 /* fs_idmapping */,
u4 /* ACL_USER */);
}
-> posix_acl_permission()
{
-1 = make_vfsuid(u0:v20000000:r65536 /* mnt_idmapping */,
&init_user_ns,
k10000004);
vfsuid_eq_kuid(-1, k10000004 /* caller_fsuid */)
}
In order to correctly map from the fs_idmapping into mnt_idmapping we
require the relevant fs_idmaping to be passed:
acl_permission_check()
-> check_acl()
-> get_acl()
-> i_op->get_acl() == fuse_get_acl()
-> posix_acl_from_xattr(u0:k10000000:r65536 /* fs_idmapping */, ...)
{
k10000004 = make_kuid(u0:k10000000:r65536 /* fs_idmapping */,
u4 /* ACL_USER */);
}
-> posix_acl_permission()
{
v20000004 = make_vfsuid(u0:v20000000:r65536 /* mnt_idmapping */,
u0:k10000000:r65536 /* fs_idmapping */,
k10000004);
vfsuid_eq_kuid(v20000004, k10000004 /* caller_fsuid */)
}
The initial_idmapping is only correct for the current situation because
all filesystems that currently support idmapped mounts do not support
being mounted with an fs_idmapping.
Note that ovl_get_acl() is used to retrieve the POSIX ACLs from the
relevant lower layer and the lower layer's mnt_idmapping needs to be
taken into account and so does the fs_idmapping. See 0c5fd887d2bb ("acl:
move idmapped mount fixup into vfs_{g,s}etxattr()") for more details.
For posix_acl_{g,s}etxattr_idmapped_mnt() it is not as obvious why the
fs_idmapping matters as it is for acl_permission_check(). Especially
because it doesn't matter for posix_acl_fix_xattr_{from,to}_user() (See
[1] for more context.).
Because posix_acl_{g,s}etxattr_idmapped_mnt() operate on the uapi
struct posix_acl_xattr_entry which contains {g,u}id_t values and thus
give the impression that the fs_idmapping is irrelevant as at this point
appropriate {g,u}id_t values have seemlingly been generated.
As we've stated multiple times this assumption is wrong and in fact the
uapi struct posix_acl_xattr_entry is taking idmappings into account
depending at what place it is operated on.
posix_acl_getxattr_idmapped_mnt()
When posix_acl_getxattr_idmapped_mnt() is called the values stored in
the uapi struct posix_acl_xattr_entry are mapped according to the
fs_idmapping. This happened when they were read from the backing store
and then translated from struct posix_acl into the uapi
struct posix_acl_xattr_entry during posix_acl_to_xattr().
In other words, the fs_idmapping matters as the values stored as
{g,u}id_t in the uapi struct posix_acl_xattr_entry have been generated
by it.
So we need to take the fs_idmapping into account during make_vfsuid()
in posix_acl_getxattr_idmapped_mnt().
posix_acl_setxattr_idmapped_mnt()
When posix_acl_setxattr_idmapped_mnt() is called the values stored as
{g,u}id_t in uapi struct posix_acl_xattr_entry are intended to be the
values that ultimately get turned back into a k{g,u}id_t in
posix_acl_from_xattr() (which turns the uapi
struct posix_acl_xattr_entry into the kernel internal struct posix_acl).
In other words, the fs_idmapping matters as the values stored as
{g,u}id_t in the uapi struct posix_acl_xattr_entry are intended to be
the values that will be undone in the fs_idmapping when writing to the
backing store.
So we need to take the fs_idmapping into account during from_vfsuid()
in posix_acl_setxattr_idmapped_mnt().
Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Fixes: 0c5fd887d2bb ("acl: move idmapped mount fixup into vfs_{g,s}etxattr()")
Cc: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Link: https://lore.kernel.org/r/20220816113514.43304-1-brauner@kernel.org
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git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs update from Miklos Szeredi:
"Just a small update"
* tag 'ovl-update-6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: fix spelling mistakes
ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh()
ovl: improve ovl_get_acl() if POSIX ACL support is off
ovl: fix some kernel-doc comments
ovl: warn if trusted xattr creation fails
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs lseek updates from Al Viro:
"Jason's lseek series.
Saner handling of 'lseek should fail with ESPIPE' - this gets rid of
the magical no_llseek thing and makes checks consistent.
In particular, the ad-hoc "can we do splice via internal pipe" checks
got saner (and somewhat more permissive, which is what Jason had been
after, AFAICT)"
* tag 'pull-work.lseek' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs: remove no_llseek
fs: check FMODE_LSEEK to control internal pipe splicing
vfio: do not set FMODE_LSEEK flag
dma-buf: remove useless FMODE_LSEEK flag
fs: do not compare against ->llseek
fs: clear or set FMODE_LSEEK based on llseek function
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fix follow spelling misktakes:
decendant ==> descendant
indentify ==> identify
underlaying ==> underlying
Reported-by: Hacash Robot <hacashRobot@santino.com>
Signed-off-by: William Dean <williamsukatube@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Some code paths cannot guarantee the inode have any dentry alias. So
WARN_ON() all !dentry may flood the kernel logs.
For example, when an overlayfs inode is watched by inotifywait (1), and
someone is trying to read the /proc/$(pidof inotifywait)/fdinfo/INOTIFY_FD,
at that time if the dentry has been reclaimed by kernel (such as
echo 2 > /proc/sys/vm/drop_caches), there will be a WARN_ON(). The
printed call stack would be like:
? show_mark_fhandle+0xf0/0xf0
show_mark_fhandle+0x4a/0xf0
? show_mark_fhandle+0xf0/0xf0
? seq_vprintf+0x30/0x50
? seq_printf+0x53/0x70
? show_mark_fhandle+0xf0/0xf0
inotify_fdinfo+0x70/0x90
show_fdinfo.isra.4+0x53/0x70
seq_show+0x130/0x170
seq_read+0x153/0x440
vfs_read+0x94/0x150
ksys_read+0x5f/0xe0
do_syscall_64+0x59/0x1e0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
So let's drop WARN_ON() to avoid kernel log flooding.
Reported-by: Hongbo Yin <yinhongbo@bytedance.com>
Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Signed-off-by: Tianci Zhang <zhangtianci.1997@bytedance.com>
Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles")
Cc: <stable@vger.kernel.org> # v4.16
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Provide a proper stub for the !CONFIG_FS_POSIX_ACL case.
Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Remove warnings found by running scripts/kernel-doc,
which is caused by using 'make W=1'.
fs/overlayfs/super.c:311: warning: Function parameter or member 'dentry'
not described in 'ovl_statfs'
fs/overlayfs/super.c:311: warning: Excess function parameter 'sb'
description in 'ovl_statfs'
fs/overlayfs/super.c:357: warning: Function parameter or member 'm' not
described in 'ovl_show_options'
fs/overlayfs/super.c:357: warning: Function parameter or member 'dentry'
not described in 'ovl_show_options'
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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When mounting overlayfs in an unprivileged user namespace, trusted xattr
creation will fail. This will lead to failures in some file operations,
e.g. in the following situation:
mkdir lower upper work merged
mkdir lower/directory
mount -toverlay -olowerdir=lower,upperdir=upper,workdir=work none merged
rmdir merged/directory
mkdir merged/directory
The last mkdir will fail:
mkdir: cannot create directory 'merged/directory': Input/output error
The cause for these failures is currently extremely non-obvious and hard to
debug. Hence, warn the user and suggest using the userxattr mount option,
if it is not already supplied and xattr creation fails during the
self-check.
Reported-by: Alois Wohlschlager <alois1@gmx-topmail.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Now vfs_llseek() can simply check for FMODE_LSEEK; if it's set,
we know that ->llseek() won't be NULL and if it's not we should
just fail with -ESPIPE.
A couple of other places where we used to check for special
values of ->llseek() (somewhat inconsistently) switched to
checking FMODE_LSEEK.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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This reverts commit 4a47c6385bb4e0786826e75bd4555aba32953653.
Now that we have a proper fix for POSIX ACLs with overlayfs on top of
idmapped layers revert the temporary fix.
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
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During permission checking overlayfs will call
ovl_permission()
-> generic_permission()
-> acl_permission_check()
-> check_acl()
-> get_acl()
-> inode->i_op->get_acl() == ovl_get_acl()
-> get_acl() /* on the underlying filesystem */
-> inode->i_op->get_acl() == /*lower filesystem callback */
-> posix_acl_permission()
passing through the get_acl() request to the underlying filesystem.
Before returning these values to the VFS we need to take the idmapping of the
relevant layer into account and translate any ACL_{GROUP,USER} values according
to the idmapped mount.
We cannot alter the ACLs returned from the relevant layer directly as that
would alter the cached values filesystem wide for the lower filesystem. Instead
we can clone the ACLs and then apply the relevant idmapping of the layer.
This is obviously only relevant when idmapped layers are used.
Link: https://lore.kernel.org/r/20220708090134.385160-4-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: linux-unionfs@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
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This cycle we added support for mounting overlayfs on top of idmapped mounts.
Recently I've started looking into potential corner cases when trying to add
additional tests and I noticed that reporting for POSIX ACLs is currently wrong
when using idmapped layers with overlayfs mounted on top of it.
I'm going to give a rather detailed explanation to both the origin of the
problem and the solution.
Let's assume the user creates the following directory layout and they have a
rootfs /var/lib/lxc/c1/rootfs. The files in this rootfs are owned as you would
expect files on your host system to be owned. For example, ~/.bashrc for your
regular user would be owned by 1000:1000 and /root/.bashrc would be owned by
0:0. IOW, this is just regular boring filesystem tree on an ext4 or xfs
filesystem.
The user chooses to set POSIX ACLs using the setfacl binary granting the user
with uid 4 read, write, and execute permissions for their .bashrc file:
setfacl -m u:4:rwx /var/lib/lxc/c2/rootfs/home/ubuntu/.bashrc
Now they to expose the whole rootfs to a container using an idmapped mount. So
they first create:
mkdir -pv /vol/contpool/{ctrover,merge,lowermap,overmap}
mkdir -pv /vol/contpool/ctrover/{over,work}
chown 10000000:10000000 /vol/contpool/ctrover/{over,work}
The user now creates an idmapped mount for the rootfs:
mount-idmapped/mount-idmapped --map-mount=b:0:10000000:65536 \
/var/lib/lxc/c2/rootfs \
/vol/contpool/lowermap
This for example makes it so that /var/lib/lxc/c2/rootfs/home/ubuntu/.bashrc
which is owned by uid and gid 1000 as being owned by uid and gid 10001000 at
/vol/contpool/lowermap/home/ubuntu/.bashrc.
Assume the user wants to expose these idmapped mounts through an overlayfs
mount to a container.
mount -t overlay overlay \
-o lowerdir=/vol/contpool/lowermap, \
upperdir=/vol/contpool/overmap/over, \
workdir=/vol/contpool/overmap/work \
/vol/contpool/merge
The user can do this in two ways:
(1) Mount overlayfs in the initial user namespace and expose it to the
container.
(2) Mount overlayfs on top of the idmapped mounts inside of the container's
user namespace.
Let's assume the user chooses the (1) option and mounts overlayfs on the host
and then changes into a container which uses the idmapping 0:10000000:65536
which is the same used for the two idmapped mounts.
Now the user tries to retrieve the POSIX ACLs using the getfacl command
getfacl -n /vol/contpool/lowermap/home/ubuntu/.bashrc
and to their surprise they see:
# file: vol/contpool/merge/home/ubuntu/.bashrc
# owner: 1000
# group: 1000
user::rw-
user:4294967295:rwx
group::r--
mask::rwx
other::r--
indicating the the uid wasn't correctly translated according to the idmapped
mount. The problem is how we currently translate POSIX ACLs. Let's inspect the
callchain in this example:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:0:4k /* initial idmapping */
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get == ovl_posix_acl_xattr_get()
| -> ovl_xattr_get()
| -> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get() /* lower filesystem callback */
|> posix_acl_fix_xattr_to_user()
{
4 = make_kuid(&init_user_ns, 4);
4 = mapped_kuid_fs(&init_user_ns /* no idmapped mount */, 4);
/* FAILURE */
-1 = from_kuid(0:10000000:65536 /* caller's idmapping */, 4);
}
If the user chooses to use option (2) and mounts overlayfs on top of idmapped
mounts inside the container things don't look that much better:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:10000000:65536
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get == ovl_posix_acl_xattr_get()
| -> ovl_xattr_get()
| -> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get() /* lower filesystem callback */
|> posix_acl_fix_xattr_to_user()
{
4 = make_kuid(&init_user_ns, 4);
4 = mapped_kuid_fs(&init_user_ns, 4);
/* FAILURE */
-1 = from_kuid(0:10000000:65536 /* caller's idmapping */, 4);
}
As is easily seen the problem arises because the idmapping of the lower mount
isn't taken into account as all of this happens in do_gexattr(). But
do_getxattr() is always called on an overlayfs mount and inode and thus cannot
possible take the idmapping of the lower layers into account.
This problem is similar for fscaps but there the translation happens as part of
vfs_getxattr() already. Let's walk through an fscaps overlayfs callchain:
setcap 'cap_net_raw+ep' /var/lib/lxc/c2/rootfs/home/ubuntu/.bashrc
The expected outcome here is that we'll receive the cap_net_raw capability as
we are able to map the uid associated with the fscap to 0 within our container.
IOW, we want to see 0 as the result of the idmapping translations.
If the user chooses option (1) we get the following callchain for fscaps:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:0:4k /* initial idmapping */
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
-> vfs_getxattr()
-> xattr_getsecurity()
-> security_inode_getsecurity() ________________________________
-> cap_inode_getsecurity() | |
{ V |
10000000 = make_kuid(0:0:4k /* overlayfs idmapping */, 10000000); |
10000000 = mapped_kuid_fs(0:0:4k /* no idmapped mount */, 10000000); |
/* Expected result is 0 and thus that we own the fscap. */ |
0 = from_kuid(0:10000000:65536 /* caller's idmapping */, 10000000); |
} |
-> vfs_getxattr_alloc() |
-> handler->get == ovl_other_xattr_get() |
-> vfs_getxattr() |
-> xattr_getsecurity() |
-> security_inode_getsecurity() |
-> cap_inode_getsecurity() |
{ |
0 = make_kuid(0:0:4k /* lower s_user_ns */, 0); |
10000000 = mapped_kuid_fs(0:10000000:65536 /* idmapped mount */, 0); |
10000000 = from_kuid(0:0:4k /* overlayfs idmapping */, 10000000); |
|____________________________________________________________________|
}
-> vfs_getxattr_alloc()
-> handler->get == /* lower filesystem callback */
And if the user chooses option (2) we get:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:10000000:65536
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
-> vfs_getxattr()
-> xattr_getsecurity()
-> security_inode_getsecurity() _______________________________
-> cap_inode_getsecurity() | |
{ V |
10000000 = make_kuid(0:10000000:65536 /* overlayfs idmapping */, 0); |
10000000 = mapped_kuid_fs(0:0:4k /* no idmapped mount */, 10000000); |
/* Expected result is 0 and thus that we own the fscap. */ |
0 = from_kuid(0:10000000:65536 /* caller's idmapping */, 10000000); |
} |
-> vfs_getxattr_alloc() |
-> handler->get == ovl_other_xattr_get() |
|-> vfs_getxattr() |
-> xattr_getsecurity() |
-> security_inode_getsecurity() |
-> cap_inode_getsecurity() |
{ |
0 = make_kuid(0:0:4k /* lower s_user_ns */, 0); |
10000000 = mapped_kuid_fs(0:10000000:65536 /* idmapped mount */, 0); |
0 = from_kuid(0:10000000:65536 /* overlayfs idmapping */, 10000000); |
|____________________________________________________________________|
}
-> vfs_getxattr_alloc()
-> handler->get == /* lower filesystem callback */
We can see how the translation happens correctly in those cases as the
conversion happens within the vfs_getxattr() helper.
For POSIX ACLs we need to do something similar. However, in contrast to fscaps
we cannot apply the fix directly to the kernel internal posix acl data
structure as this would alter the cached values and would also require a rework
of how we currently deal with POSIX ACLs in general which almost never take the
filesystem idmapping into account (the noteable exception being FUSE but even
there the implementation is special) and instead retrieve the raw values based
on the initial idmapping.
The correct values are then generated right before returning to userspace. The
fix for this is to move taking the mount's idmapping into account directly in
vfs_getxattr() instead of having it be part of posix_acl_fix_xattr_to_user().
To this end we split out two small and unexported helpers
posix_acl_getxattr_idmapped_mnt() and posix_acl_setxattr_idmapped_mnt(). The
former to be called in vfs_getxattr() and the latter to be called in
vfs_setxattr().
Let's go back to the original example. Assume the user chose option (1) and
mounted overlayfs on top of idmapped mounts on the host:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:0:4k /* initial idmapping */
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| |> __vfs_getxattr()
| | -> handler->get == ovl_posix_acl_xattr_get()
| | -> ovl_xattr_get()
| | -> vfs_getxattr()
| | |> __vfs_getxattr()
| | | -> handler->get() /* lower filesystem callback */
| | |> posix_acl_getxattr_idmapped_mnt()
| | {
| | 4 = make_kuid(&init_user_ns, 4);
| | 10000004 = mapped_kuid_fs(0:10000000:65536 /* lower idmapped mount */, 4);
| | 10000004 = from_kuid(&init_user_ns, 10000004);
| | |_______________________
| | } |
| | |
| |> posix_acl_getxattr_idmapped_mnt() |
| { |
| V
| 10000004 = make_kuid(&init_user_ns, 10000004);
| 10000004 = mapped_kuid_fs(&init_user_ns /* no idmapped mount */, 10000004);
| 10000004 = from_kuid(&init_user_ns, 10000004);
| } |_________________________________________________
| |
| |
|> posix_acl_fix_xattr_to_user() |
{ V
10000004 = make_kuid(0:0:4k /* init_user_ns */, 10000004);
/* SUCCESS */
4 = from_kuid(0:10000000:65536 /* caller's idmapping */, 10000004);
}
And similarly if the user chooses option (1) and mounted overayfs on top of
idmapped mounts inside the container:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:10000000:65536
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| |> __vfs_getxattr()
| | -> handler->get == ovl_posix_acl_xattr_get()
| | -> ovl_xattr_get()
| | -> vfs_getxattr()
| | |> __vfs_getxattr()
| | | -> handler->get() /* lower filesystem callback */
| | |> posix_acl_getxattr_idmapped_mnt()
| | {
| | 4 = make_kuid(&init_user_ns, 4);
| | 10000004 = mapped_kuid_fs(0:10000000:65536 /* lower idmapped mount */, 4);
| | 10000004 = from_kuid(&init_user_ns, 10000004);
| | |_______________________
| | } |
| | |
| |> posix_acl_getxattr_idmapped_mnt() |
| { V
| 10000004 = make_kuid(&init_user_ns, 10000004);
| 10000004 = mapped_kuid_fs(&init_user_ns /* no idmapped mount */, 10000004);
| 10000004 = from_kuid(0(&init_user_ns, 10000004);
| |_________________________________________________
| } |
| |
|> posix_acl_fix_xattr_to_user() |
{ V
10000004 = make_kuid(0:0:4k /* init_user_ns */, 10000004);
/* SUCCESS */
4 = from_kuid(0:10000000:65536 /* caller's idmappings */, 10000004);
}
The last remaining problem we need to fix here is ovl_get_acl(). During
ovl_permission() overlayfs will call:
ovl_permission()
-> generic_permission()
-> acl_permission_check()
-> check_acl()
-> get_acl()
-> inode->i_op->get_acl() == ovl_get_acl()
> get_acl() /* on the underlying filesystem)
->inode->i_op->get_acl() == /*lower filesystem callback */
-> posix_acl_permission()
passing through the get_acl request to the underlying filesystem. This will
retrieve the acls stored in the lower filesystem without taking the idmapping
of the underlying mount into account as this would mean altering the cached
values for the lower filesystem. So we block using ACLs for now until we
decided on a nice way to fix this. Note this limitation both in the
documentation and in the code.
The most straightforward solution would be to have ovl_get_acl() simply
duplicate the ACLs, update the values according to the idmapped mount and
return it to acl_permission_check() so it can be used in posix_acl_permission()
forgetting them afterwards. This is a bit heavy handed but fairly
straightforward otherwise.
Link: https://github.com/brauner/mount-idmapped/issues/9
Link: https://lore.kernel.org/r/20220708090134.385160-2-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
|
|
ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs into fs.idmapped.overlay.acl
Bring in Miklos' tree which contains the temporary fix for POSIX ACLs
with overlayfs on top of idmapped layers. We will add a proper fix on
top of it and then revert the temporary fix.
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
|
|
This cycle we added support for mounting overlayfs on top of idmapped
mounts. Recently I've started looking into potential corner cases when
trying to add additional tests and I noticed that reporting for POSIX ACLs
is currently wrong when using idmapped layers with overlayfs mounted on top
of it.
I have sent out an patch that fixes this and makes POSIX ACLs work
correctly but the patch is a bit bigger and we're already at -rc5 so I
recommend we simply don't raise SB_POSIXACL when idmapped layers are
used. Then we can fix the VFS part described below for the next merge
window so we can have good exposure in -next.
I'm going to give a rather detailed explanation to both the origin of the
problem and mention the solution so people know what's going on.
Let's assume the user creates the following directory layout and they have
a rootfs /var/lib/lxc/c1/rootfs. The files in this rootfs are owned as you
would expect files on your host system to be owned. For example, ~/.bashrc
for your regular user would be owned by 1000:1000 and /root/.bashrc would
be owned by 0:0. IOW, this is just regular boring filesystem tree on an
ext4 or xfs filesystem.
The user chooses to set POSIX ACLs using the setfacl binary granting the
user with uid 4 read, write, and execute permissions for their .bashrc
file:
setfacl -m u:4:rwx /var/lib/lxc/c2/rootfs/home/ubuntu/.bashrc
Now they to expose the whole rootfs to a container using an idmapped
mount. So they first create:
mkdir -pv /vol/contpool/{ctrover,merge,lowermap,overmap}
mkdir -pv /vol/contpool/ctrover/{over,work}
chown 10000000:10000000 /vol/contpool/ctrover/{over,work}
The user now creates an idmapped mount for the rootfs:
mount-idmapped/mount-idmapped --map-mount=b:0:10000000:65536 \
/var/lib/lxc/c2/rootfs \
/vol/contpool/lowermap
This for example makes it so that
/var/lib/lxc/c2/rootfs/home/ubuntu/.bashrc which is owned by uid and gid
1000 as being owned by uid and gid 10001000 at
/vol/contpool/lowermap/home/ubuntu/.bashrc.
Assume the user wants to expose these idmapped mounts through an overlayfs
mount to a container.
mount -t overlay overlay \
-o lowerdir=/vol/contpool/lowermap, \
upperdir=/vol/contpool/overmap/over, \
workdir=/vol/contpool/overmap/work \
/vol/contpool/merge
The user can do this in two ways:
(1) Mount overlayfs in the initial user namespace and expose it to the
container.
(2) Mount overlayfs on top of the idmapped mounts inside of the container's
user namespace.
Let's assume the user chooses the (1) option and mounts overlayfs on the
host and then changes into a container which uses the idmapping
0:10000000:65536 which is the same used for the two idmapped mounts.
Now the user tries to retrieve the POSIX ACLs using the getfacl command
getfacl -n /vol/contpool/lowermap/home/ubuntu/.bashrc
and to their surprise they see:
# file: vol/contpool/merge/home/ubuntu/.bashrc
# owner: 1000
# group: 1000
user::rw-
user:4294967295:rwx
group::r--
mask::rwx
other::r--
indicating the uid wasn't correctly translated according to the idmapped
mount. The problem is how we currently translate POSIX ACLs. Let's inspect
the callchain in this example:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:0:4k /* initial idmapping */
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get == ovl_posix_acl_xattr_get()
| -> ovl_xattr_get()
| -> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get() /* lower filesystem callback */
|> posix_acl_fix_xattr_to_user()
{
4 = make_kuid(&init_user_ns, 4);
4 = mapped_kuid_fs(&init_user_ns /* no idmapped mount */, 4);
/* FAILURE */
-1 = from_kuid(0:10000000:65536 /* caller's idmapping */, 4);
}
If the user chooses to use option (2) and mounts overlayfs on top of
idmapped mounts inside the container things don't look that much better:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:10000000:65536
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get == ovl_posix_acl_xattr_get()
| -> ovl_xattr_get()
| -> vfs_getxattr()
| -> __vfs_getxattr()
| -> handler->get() /* lower filesystem callback */
|> posix_acl_fix_xattr_to_user()
{
4 = make_kuid(&init_user_ns, 4);
4 = mapped_kuid_fs(&init_user_ns, 4);
/* FAILURE */
-1 = from_kuid(0:10000000:65536 /* caller's idmapping */, 4);
}
As is easily seen the problem arises because the idmapping of the lower
mount isn't taken into account as all of this happens in do_gexattr(). But
do_getxattr() is always called on an overlayfs mount and inode and thus
cannot possible take the idmapping of the lower layers into account.
This problem is similar for fscaps but there the translation happens as
part of vfs_getxattr() already. Let's walk through an fscaps overlayfs
callchain:
setcap 'cap_net_raw+ep' /var/lib/lxc/c2/rootfs/home/ubuntu/.bashrc
The expected outcome here is that we'll receive the cap_net_raw capability
as we are able to map the uid associated with the fscap to 0 within our
container. IOW, we want to see 0 as the result of the idmapping
translations.
If the user chooses option (1) we get the following callchain for fscaps:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:0:4k /* initial idmapping */
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
-> vfs_getxattr()
-> xattr_getsecurity()
-> security_inode_getsecurity() ________________________________
-> cap_inode_getsecurity() | |
{ V |
10000000 = make_kuid(0:0:4k /* overlayfs idmapping */, 10000000); |
10000000 = mapped_kuid_fs(0:0:4k /* no idmapped mount */, 10000000); |
/* Expected result is 0 and thus that we own the fscap. */ |
0 = from_kuid(0:10000000:65536 /* caller's idmapping */, 10000000); |
} |
-> vfs_getxattr_alloc() |
-> handler->get == ovl_other_xattr_get() |
-> vfs_getxattr() |
-> xattr_getsecurity() |
-> security_inode_getsecurity() |
-> cap_inode_getsecurity() |
{ |
0 = make_kuid(0:0:4k /* lower s_user_ns */, 0); |
10000000 = mapped_kuid_fs(0:10000000:65536 /* idmapped mount */, 0); |
10000000 = from_kuid(0:0:4k /* overlayfs idmapping */, 10000000); |
|____________________________________________________________________|
}
-> vfs_getxattr_alloc()
-> handler->get == /* lower filesystem callback */
And if the user chooses option (2) we get:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:10000000:65536
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
-> vfs_getxattr()
-> xattr_getsecurity()
-> security_inode_getsecurity() _______________________________
-> cap_inode_getsecurity() | |
{ V |
10000000 = make_kuid(0:10000000:65536 /* overlayfs idmapping */, 0); |
10000000 = mapped_kuid_fs(0:0:4k /* no idmapped mount */, 10000000); |
/* Expected result is 0 and thus that we own the fscap. */ |
0 = from_kuid(0:10000000:65536 /* caller's idmapping */, 10000000); |
} |
-> vfs_getxattr_alloc() |
-> handler->get == ovl_other_xattr_get() |
|-> vfs_getxattr() |
-> xattr_getsecurity() |
-> security_inode_getsecurity() |
-> cap_inode_getsecurity() |
{ |
0 = make_kuid(0:0:4k /* lower s_user_ns */, 0); |
10000000 = mapped_kuid_fs(0:10000000:65536 /* idmapped mount */, 0); |
0 = from_kuid(0:10000000:65536 /* overlayfs idmapping */, 10000000); |
|____________________________________________________________________|
}
-> vfs_getxattr_alloc()
-> handler->get == /* lower filesystem callback */
We can see how the translation happens correctly in those cases as the
conversion happens within the vfs_getxattr() helper.
For POSIX ACLs we need to do something similar. However, in contrast to
fscaps we cannot apply the fix directly to the kernel internal posix acl
data structure as this would alter the cached values and would also require
a rework of how we currently deal with POSIX ACLs in general which almost
never take the filesystem idmapping into account (the noteable exception
being FUSE but even there the implementation is special) and instead
retrieve the raw values based on the initial idmapping.
The correct values are then generated right before returning to
userspace. The fix for this is to move taking the mount's idmapping into
account directly in vfs_getxattr() instead of having it be part of
posix_acl_fix_xattr_to_user().
To this end we simply move the idmapped mount translation into a separate
step performed in vfs_{g,s}etxattr() instead of in
posix_acl_fix_xattr_{from,to}_user().
To see how this fixes things let's go back to the original example. Assume
the user chose option (1) and mounted overlayfs on top of idmapped mounts
on the host:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:0:4k /* initial idmapping */
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| |> __vfs_getxattr()
| | -> handler->get == ovl_posix_acl_xattr_get()
| | -> ovl_xattr_get()
| | -> vfs_getxattr()
| | |> __vfs_getxattr()
| | | -> handler->get() /* lower filesystem callback */
| | |> posix_acl_getxattr_idmapped_mnt()
| | {
| | 4 = make_kuid(&init_user_ns, 4);
| | 10000004 = mapped_kuid_fs(0:10000000:65536 /* lower idmapped mount */, 4);
| | 10000004 = from_kuid(&init_user_ns, 10000004);
| | |_______________________
| | } |
| | |
| |> posix_acl_getxattr_idmapped_mnt() |
| { |
| V
| 10000004 = make_kuid(&init_user_ns, 10000004);
| 10000004 = mapped_kuid_fs(&init_user_ns /* no idmapped mount */, 10000004);
| 10000004 = from_kuid(&init_user_ns, 10000004);
| } |_________________________________________________
| |
| |
|> posix_acl_fix_xattr_to_user() |
{ V
10000004 = make_kuid(0:0:4k /* init_user_ns */, 10000004);
/* SUCCESS */
4 = from_kuid(0:10000000:65536 /* caller's idmapping */, 10000004);
}
And similarly if the user chooses option (1) and mounted overayfs on top of
idmapped mounts inside the container:
idmapped mount /vol/contpool/merge: 0:10000000:65536
caller's idmapping: 0:10000000:65536
overlayfs idmapping (ofs->creator_cred): 0:10000000:65536
sys_getxattr()
-> path_getxattr()
-> getxattr()
-> do_getxattr()
|> vfs_getxattr()
| |> __vfs_getxattr()
| | -> handler->get == ovl_posix_acl_xattr_get()
| | -> ovl_xattr_get()
| | -> vfs_getxattr()
| | |> __vfs_getxattr()
| | | -> handler->get() /* lower filesystem callback */
| | |> posix_acl_getxattr_idmapped_mnt()
| | {
| | 4 = make_kuid(&init_user_ns, 4);
| | 10000004 = mapped_kuid_fs(0:10000000:65536 /* lower idmapped mount */, 4);
| | 10000004 = from_kuid(&init_user_ns, 10000004);
| | |_______________________
| | } |
| | |
| |> posix_acl_getxattr_idmapped_mnt() |
| { V
| 10000004 = make_kuid(&init_user_ns, 10000004);
| 10000004 = mapped_kuid_fs(&init_user_ns /* no idmapped mount */, 10000004);
| 10000004 = from_kuid(0(&init_user_ns, 10000004);
| |_________________________________________________
| } |
| |
|> posix_acl_fix_xattr_to_user() |
{ V
10000004 = make_kuid(0:0:4k /* init_user_ns */, 10000004);
/* SUCCESS */
4 = from_kuid(0:10000000:65536 /* caller's idmappings */, 10000004);
}
The last remaining problem we need to fix here is ovl_get_acl(). During
ovl_permission() overlayfs will call:
ovl_permission()
-> generic_permission()
-> acl_permission_check()
-> check_acl()
-> get_acl()
-> inode->i_op->get_acl() == ovl_get_acl()
> get_acl() /* on the underlying filesystem)
->inode->i_op->get_acl() == /*lower filesystem callback */
-> posix_acl_permission()
passing through the get_acl request to the underlying filesystem. This will
retrieve the acls stored in the lower filesystem without taking the
idmapping of the underlying mount into account as this would mean altering
the cached values for the lower filesystem. The simple solution is to have
ovl_get_acl() simply duplicate the ACLs, update the values according to the
idmapped mount and return it to acl_permission_check() so it can be used in
posix_acl_permission(). Since overlayfs doesn't cache ACLs they'll be
released right after.
Link: https://github.com/brauner/mount-idmapped/issues/9
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: linux-unionfs@vger.kernel.org
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Fixes: bc70682a497c ("ovl: support idmapped layers")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Now that we introduced new infrastructure to increase the type safety
for filesystems supporting idmapped mounts port the first part of the
vfs over to them.
This ports the attribute changes codepaths to rely on the new better
helpers using a dedicated type.
Before this change we used to take a shortcut and place the actual
values that would be written to inode->i_{g,u}id into struct iattr. This
had the advantage that we moved idmappings mostly out of the picture
early on but it made reasoning about changes more difficult than it
should be.
The filesystem was never explicitly told that it dealt with an idmapped
mount. The transition to the value that needed to be stored in
inode->i_{g,u}id appeared way too early and increased the probability of
bugs in various codepaths.
We know place the same value in struct iattr no matter if this is an
idmapped mount or not. The vfs will only deal with type safe
vfs{g,u}id_t. This makes it massively safer to perform permission checks
as the type will tell us what checks we need to perform and what helpers
we need to use.
Fileystems raising FS_ALLOW_IDMAP can't simply write ia_vfs{g,u}id to
inode->i_{g,u}id since they are different types. Instead they need to
use the dedicated vfs{g,u}id_to_k{g,u}id() helpers that map the
vfs{g,u}id into the filesystem.
The other nice effect is that filesystems like overlayfs don't need to
care about idmappings explicitly anymore and can simply set up struct
iattr accordingly directly.
Link: https://lore.kernel.org/lkml/CAHk-=win6+ahs1EwLkcq8apqLi_1wXFWbrPf340zYEhObpz4jA@mail.gmail.com [1]
Link: https://lore.kernel.org/r/20220621141454.2914719-9-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs updates from Miklos Szeredi:
- Support idmapped layers in overlayfs (Christian Brauner)
- Add a fix to exportfs that is relevant to open_by_handle_at(2) as
well
- Introduce new lookup helpers that allow passing mnt_userns into
inode_permission()
* tag 'ovl-update-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: support idmapped layers
ovl: handle idmappings in ovl_xattr_{g,s}et()
ovl: handle idmappings in layer open helpers
ovl: handle idmappings in ovl_permission()
ovl: use ovl_copy_{real,upper}attr() wrappers
ovl: store lower path in ovl_inode
ovl: handle idmappings for layer lookup
ovl: handle idmappings for layer fileattrs
ovl: use ovl_path_getxattr() wrapper
ovl: use ovl_lookup_upper() wrapper
ovl: use ovl_do_notify_change() wrapper
ovl: pass layer mnt to ovl_open_realfile()
ovl: pass ofs to setattr operations
ovl: handle idmappings in creation operations
ovl: add ovl_upper_mnt_userns() wrapper
ovl: pass ofs to creation operations
ovl: use wrappers to all vfs_*xattr() calls
exportfs: support idmapped mounts
fs: add two trivial lookup helpers
|
|
Currently various places test if direct IO is possible on a file by
checking for the existence of the direct_IO address space operation.
This is a poor choice, as the direct_IO operation may not be used - it is
only used if the generic_file_*_iter functions are called for direct IO
and some filesystems - particularly NFS - don't do this.
Instead, introduce a new f_mode flag: FMODE_CAN_ODIRECT and change the
various places to check this (avoiding pointer dereferences).
do_dentry_open() will set this flag if ->direct_IO is present, so
filesystems do not need to be changed.
NFS *is* changed, to set the flag explicitly and discard the direct_IO
entry in the address_space_operations for files.
Other filesystems which currently use noop_direct_IO could usefully be
changed to set this flag instead.
Link: https://lkml.kernel.org/r/164859778128.29473.15189737957277399416.stgit@noble.brown
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: NeilBrown <neilb@suse.de>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Now that overlay is able to take a layers idmapping into account allow
overlay mounts to be created on top of idmapped mounts.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
When retrieving xattrs from the upper or lower layers take the relevant
mount's idmapping into account. We rely on the previously introduced
ovl_i_path_real() helper to retrieve the relevant path. This is needed
to support idmapped base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
In earlier patches we already passed down the relevant upper or lower
path to ovl_open_realfile(). Now let the open helpers actually take the
idmapping of the relevant mount into account when checking permissions.
This is needed to support idmapped base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Use the previously introduced ovl_i_path_real() helper to retrieve the
relevant upper or lower path and take the mount's idmapping into account
for the lower layer permission check. This is needed to support idmapped
base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
When copying inode attributes from the upper or lower layer to ovl inodes
we need to take the upper or lower layer's mount's idmapping into
account. In a lot of places we call ovl_copyattr() only on upper inodes and
in some we call it on either upper or lower inodes. Split this into two
separate helpers.
The first one should only be called on upper
inodes and is thus called ovl_copy_upperattr(). The second one can be
called on upper or lower inodes. We add ovl_copy_realattr() for this
task. The new helper makes use of the previously added ovl_i_path_real()
helper. This is needed to support idmapped base layers with overlay.
When overlay copies the inode information from an upper or lower layer
to the relevant overlay inode it will apply the idmapping of the upper
or lower layer when doing so. The ovl inode ownership will thus always
correctly reflect the ownership of the idmapped upper or lower layer.
All idmapping helpers are nops when no idmapped base layers are used.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Create some ovl_i_* helpers to get real path from ovl inode. Instead of
just stashing struct inode for the lower layer we stash struct path for
the lower layer. The helpers allow to retrieve a struct path for the
relevant upper or lower layer. This will be used when retrieving
information based on struct inode when copying up inode attributes from
upper or lower inodes to ovl inodes and when checking permissions in
ovl_permission() in following patches. This is needed to support
idmapped base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Make the two places where lookup helpers can be called either on lower
or upper layers take the mount's idmapping into account. To this end we
pass down the mount in struct ovl_lookup_data. It can later also be used
to construct struct path for various other helpers. This is needed to
support idmapped base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Take the upper mount's idmapping into account when setting fileattrs on
the upper layer. This is needed to support idmapped base layers with
overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Add a helper that allows to retrieve ovl xattrs from either lower or
upper layers. To stop passing mnt and dentry separately everywhere use
struct path which more accurately reflects the tight coupling between
mount and dentry in this helper. Swich over all places to pass a path
argument that can operate on either upper or lower layers. This is
needed to support idmapped base layers with overlayfs.
Some helpers are always called with an upper dentry, which is now utilized
by these helpers to create the path. Make this usage explicit by renaming
the argument to "upperdentry" and by renaming the function as well in some
cases. Also add a check in ovl_do_getxattr() to catch misuse of these
functions.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Introduce ovl_lookup_upper() as a simple wrapper around lookup_one().
Make it clear in the helper's name that this only operates on the upper
layer. The wrapper will take upper layer's idmapping into account when
checking permission in lookup_one().
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Introduce ovl_do_notify_change() as a simple wrapper around
notify_change() to support idmapped layers. The helper mirrors other
ovl_do_*() helpers that operate on the upper layers.
When changing ownership of an upper object the intended ownership needs
to be mapped according to the upper layer's idmapping. This mapping is
the inverse to the mapping applied when copying inode information from
an upper layer to the corresponding overlay inode. So e.g., when an
upper mount maps files that are stored on-disk as owned by id 1001 to
1000 this means that calling stat on this object from an idmapped mount
will report the file as being owned by id 1000. Consequently in order to
change ownership of an object in this filesystem so it appears as being
owned by id 1000 in the upper idmapped layer it needs to store id 1001
on disk. The mnt mapping helpers take care of this.
All idmapping helpers are nops when no idmapped base layers are used.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Ensure that ovl_open_realfile() takes the mount's idmapping into
account. We add a new helper ovl_path_realdata() that can be used to
easily retrieve the relevant path which we can pass down. This is needed
to support idmapped base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Pass down struct ovl_fs to setattr operations so we can ultimately
retrieve the relevant upper mount and take the mount's idmapping into
account when creating new filesystem objects. This is needed to support
idmapped base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
When creating objects in the upper layer we need to pass down the upper
idmapping into the respective vfs helpers in order to support idmapped
base layers. The vfs helpers will take care of the rest.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Add a tiny wrapper to retrieve the upper mount's idmapping. Have it
return the initial idmapping until we have prepared and converted all
places to take the relevant idmapping into account. Then we can switch
on idmapped layer support by having ovl_upper_mnt_userns() return the
upper mount's idmapping.
Suggested-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Pass down struct ovl_fs to all creation helpers so we can ultimately
retrieve the relevant upper mount and take the mount's idmapping into
account when creating new filesystem objects. This is needed to support
idmapped base layers with overlay.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
|
Use helpers ovl_*xattr() to access user/trusted.overlay.* xattrs
and use helpers ovl_do_*xattr() to access generic xattrs. This is a
preparatory patch for using idmapped base layers with overlay.
Note that a few of those places called vfs_*xattr() calls directly to
reduce the amount of debug output. But as Miklos pointed out since
overlayfs has been stable for quite some time the debug output isn't all
that relevant anymore and the additional debug in all locations was
actually quite helpful when developing this patch series.
Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
|
