diff options
| author | Peter Griffin | 2022-11-03 17:02:10 +0000 |
|---|---|---|
| committer | Al Viro | 2022-11-19 02:22:11 -0500 |
| commit | 406c706c7b7f1730aa787e914817b8d16b1e99f6 (patch) | |
| tree | 570db537a1ab34e0ab06c8d5adc8a31e031e11c7 /fs | |
| parent | 7ee47dcfff1835ff75a794d1075b6b5f5462cfed (diff) | |
vfs: vfs_tmpfile: ensure O_EXCL flag is enforced
If O_EXCL is *not* specified, then linkat() can be
used to link the temporary file into the filesystem.
If O_EXCL is specified then linkat() should fail (-1).
After commit 863f144f12ad ("vfs: open inside ->tmpfile()")
the O_EXCL flag is no longer honored by the vfs layer for
tmpfile, which means the file can be linked even if O_EXCL
flag is specified, which is a change in behaviour for
userspace!
The open flags was previously passed as a parameter, so it
was uneffected by the changes to file->f_flags caused by
finish_open(). This patch fixes the issue by storing
file->f_flags in a local variable so the O_EXCL test
logic is restored.
This regression was detected by Android CTS Bionic fcntl()
tests running on android-mainline [1].
[1] https://android.googlesource.com/platform/bionic/+/
refs/heads/master/tests/fcntl_test.cpp#352
Fixes: 863f144f12ad ("vfs: open inside ->tmpfile()")
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Tested-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/namei.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/namei.c b/fs/namei.c index 578c2110df02..9155ecb547ce 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3591,6 +3591,7 @@ static int vfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir = d_inode(parentpath->dentry); struct inode *inode; int error; + int open_flag = file->f_flags; /* we want directory to be writable */ error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC); @@ -3613,7 +3614,7 @@ static int vfs_tmpfile(struct user_namespace *mnt_userns, if (error) return error; inode = file_inode(file); - if (!(file->f_flags & O_EXCL)) { + if (!(open_flag & O_EXCL)) { spin_lock(&inode->i_lock); inode->i_state |= I_LINKABLE; spin_unlock(&inode->i_lock); |