diff options
| author | Mickaël Salaün | 2024-05-16 20:19:34 +0200 |
|---|---|---|
| committer | Mickaël Salaün | 2024-05-31 16:41:52 +0200 |
| commit | 88da52ccd66e65f2e63a6c35c9dff55d448ef4dc (patch) | |
| tree | 4308738f019d2b37b3035db93ff5b77cf79b0a6a /security | |
| parent | 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0 (diff) | |
landlock: Fix d_parent walk
The WARN_ON_ONCE() in collect_domain_accesses() can be triggered when
trying to link a root mount point. This cannot work in practice because
this directory is mounted, but the VFS check is done after the call to
security_path_link().
Do not use source directory's d_parent when the source directory is the
mount point.
Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: stable@vger.kernel.org
Reported-by: syzbot+bf4903dc7e12b18ebc87@syzkaller.appspotmail.com
Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER")
Closes: https://lore.kernel.org/r/000000000000553d3f0618198200@google.com
Link: https://lore.kernel.org/r/20240516181935.1645983-2-mic@digikod.net
[mic: Fix commit message]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Diffstat (limited to 'security')
| -rw-r--r-- | security/landlock/fs.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 22d8b7c28074..7877a64cc6b8 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -1110,6 +1110,7 @@ static int current_check_refer_path(struct dentry *const old_dentry, bool allow_parent1, allow_parent2; access_mask_t access_request_parent1, access_request_parent2; struct path mnt_dir; + struct dentry *old_parent; layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS] = {}, layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS] = {}; @@ -1157,9 +1158,17 @@ static int current_check_refer_path(struct dentry *const old_dentry, mnt_dir.mnt = new_dir->mnt; mnt_dir.dentry = new_dir->mnt->mnt_root; + /* + * old_dentry may be the root of the common mount point and + * !IS_ROOT(old_dentry) at the same time (e.g. with open_tree() and + * OPEN_TREE_CLONE). We do not need to call dget(old_parent) because + * we keep a reference to old_dentry. + */ + old_parent = (old_dentry == mnt_dir.dentry) ? old_dentry : + old_dentry->d_parent; + /* new_dir->dentry is equal to new_dentry->d_parent */ - allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, - old_dentry->d_parent, + allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, old_parent, &layer_masks_parent1); allow_parent2 = collect_domain_accesses( dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2); |