On Mon, Sep 4, 2023 at 6:44 AM Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > On Mon, 4 Sept 2023 at 15:24, Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > 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. > > > > Reported-by: Ruiwen Zhao <ruiwen@xxxxxxxxxx> > > Link: https://lore.kernel.org/r/CAKd=y5Hpg7J2gxrFT02F94o=FM9QvGp=kcH1Grctx8HzFYvpiA@xxxxxxxxxxxxxx/ > > Fixes: 72db82115d2b ("ovl: copy up sync/noatime fileattr flags") > > Cc: <stable@xxxxxxxxxxxxxxx> # v5.15 > > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> > > --- > > > > Hi Miklos, > > > > Do you agree with this solution? > > It's good enough. Linux might add API's in the future that allow > querying and setting fileattr on symlinks, but we can deal with that > later. > > Thanks, > Miklos Thanks Amir for sending the fix! The fix looks good but I am not sure how to LGTM it. (Still new to the kernel review process) I believe the fix will be merged to the master branch first. Can we backport it to 5.15, considering this is a regression and 5.15 is an LTS version? Thanks, Ruiwen
