tree 694fc33fb69fd027756b9b1d21c2c4d8b3372b6a
parent 2e9beb0bcb334ea993646ffeaa28aa67fe716ff9
author Amir Goldstein <amir73il@gmail.com> 1693833881 +0300
committer COS Cherry Picker <cloud-image-release@prod.google.com> 1694216413 -0700

ovl: fix failed copyup of fileattr on a symlink

Some local filesystems support setting persistent fileattr flags
(e.g. FS_NOATIME_FL) on directories and regular files via ioctl.
Some of those persistent fileattr flags are reflected to vfs as
in-memory inode flags (e.g. S_NOATIME).

Overlayfs uses the in-memory inode flags (e.g. S_NOATIME) on a lower file
as an indication that a the lower file may have persistent inode fileattr
flags (e.g. FS_NOATIME_FL) that need to be copied to upper file.

However, in some cases, the S_NOATIME in-memory flag could be a false
indication for persistent FS_NOATIME_FL fileattr. For example, with NFS
and FUSE lower fs, as was the case in the two bug reports, the S_NOATIME
flag is set unconditionally for all inodes.

Users cannot set persistent fileattr flags on symlinks and special files,
but in some local fs, such as ext4/btrfs/tmpfs, the FS_NOATIME_FL fileattr
flag are inheritted to symlinks and special files from parent directory.

In both cases described above, when lower symlink has the S_NOATIME flag,
overlayfs will try to copy the symlink's fileattrs and fail with error
ENOXIO, because it could not open the symlink for the ioctl security hook.

To solve this failure, do not attempt to copyup fileattrs for anything
other than directories and regular files.

BUG=b/299359599
TEST=presubmit
RELEASE_NOTE=Fixed failed copyup of fileattr on a symlink.

cos-patch: bug
Reported-by: Ruiwen Zhao <ruiwen@google.com>
Link: https://lore.kernel.org/r/CAKd=y5Hpg7J2gxrFT02F94o=FM9QvGp=kcH1Grctx8HzFYvpiA@mail.gmail.com/
Fixes: 72db82115d2b ("ovl: copy up sync/noatime fileattr flags")
Cc: <stable@vger.kernel.org> # v5.15
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Change-Id: Ic353c5a705c429ec5c14850d7376b060448f4e68
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/56988
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>