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

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>

1 files changed, 29 insertions, 0 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 0369eb22c1bb..e4c2da4566f1 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -690,6 +690,7 @@ xfs_inode_inherit_flags(
 	const struct xfs_inode	*pip)
 {
 	unsigned int		di_flags = 0;
+	xfs_failaddr_t		failaddr;
 	umode_t			mode = VFS_I(ip)->i_mode;
 
 	if (S_ISDIR(mode)) {
@@ -729,6 +730,24 @@ xfs_inode_inherit_flags(
 		di_flags |= XFS_DIFLAG_FILESTREAM;
 
 	ip->i_diflags |= di_flags;
+
+	/*
+	 * Inode verifiers on older kernels only check that the extent size
+	 * hint is an integer multiple of the rt extent size on realtime files.
+	 * They did not check the hint alignment on a directory with both
+	 * rtinherit and extszinherit flags set.  If the misaligned hint is
+	 * propagated from a directory into a new realtime file, new file
+	 * allocations will fail due to math errors in the rt allocator and/or
+	 * trip the verifiers.  Validate the hint settings in the new file so
+	 * that we don't let broken hints propagate.
+	 */
+	failaddr = xfs_inode_validate_extsize(ip->i_mount, ip->i_extsize,
+			VFS_I(ip)->i_mode, ip->i_diflags);
+	if (failaddr) {
+		ip->i_diflags &= ~(XFS_DIFLAG_EXTSIZE |
+				   XFS_DIFLAG_EXTSZINHERIT);
+		ip->i_extsize = 0;
+	}
 }
 
 /* Propagate di_flags2 from a parent inode to a child inode. */
@@ -737,12 +756,22 @@ xfs_inode_inherit_flags2(
 	struct xfs_inode	*ip,
 	const struct xfs_inode	*pip)
 {
+	xfs_failaddr_t		failaddr;
+
 	if (pip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE) {
 		ip->i_diflags2 |= XFS_DIFLAG2_COWEXTSIZE;
 		ip->i_cowextsize = pip->i_cowextsize;
 	}
 	if (pip->i_diflags2 & XFS_DIFLAG2_DAX)
 		ip->i_diflags2 |= XFS_DIFLAG2_DAX;
+
+	/* Don't let invalid cowextsize hints propagate. */
+	failaddr = xfs_inode_validate_cowextsize(ip->i_mount, ip->i_cowextsize,
+			VFS_I(ip)->i_mode, ip->i_diflags, ip->i_diflags2);
+	if (failaddr) {
+		ip->i_diflags2 &= ~XFS_DIFLAG2_COWEXTSIZE;
+		ip->i_cowextsize = 0;
+	}
 }
 
 /*