tree e14b31ce03250f8f87230b89d704b25f4cbe0d2b
parent 3646eb3c975fa8afc3cf0e18d846b9bee251c1d9
author Darrick J. Wong <djwong@kernel.org> 1622418477 -0700
committer Darrick J. Wong <djwong@kernel.org> 1623887164 -0700

xfs: validate extsz hints against rt extent size when rtinherit is set

Source kernel commit: 603f000b15f21ce8932f76689c7aa9fe58261cf5

The RTINHERIT bit can be set on a directory so that newly created
regular files will have the REALTIME bit set to store their data on the
realtime volume.  If an extent size hint (and EXTSZINHERIT) are set on
the directory, the hint will also be copied into the new file.

As pointed out in previous patches, for realtime files we require the
extent size hint be an integer multiple of the realtime extent, but we
don't perform the same validation on a directory with both RTINHERIT and
EXTSZINHERIT set, even though the only use-case of that combination is
to propagate extent size hints into new realtime files.  This leads to
inode corruption errors when the bad values are propagated.

Because there may be existing filesystems with such a configuration, we
cannot simply amend the inode verifier to trip on these directories and
call it a day because that will cause previously "working" filesystems
to start throwing errors abruptly.  Note that it's valid to have
directories with rtinherit set even if there is no realtime volume, in
which case the problem does not manifest because rtinherit is ignored if
there's no realtime device; and it's possible that someone set the flag,
crashed, repaired the filesystem (which clears the hint on the realtime
file) and continued.

Therefore, mitigate this issue in several ways: First, if we try to
write out an inode with both rtinherit/extszinherit set and an unaligned
extent size hint, turn off the hint to correct the error.  Second, if
someone tries to misconfigure a directory via the fssetxattr ioctl, fail
the ioctl.  Third, reverify both extent size hint values when we
propagate heritable inode attributes from parent to child, to prevent
misconfigurations from spreading.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>