[PATCH 5.15 057/148] xfs: validate inode fork size against fork format

Greg Kroah-Hartman
2022-09-26T11:19:50Z

From: Dave Chinner <dchinner@redhat.com>

[ Upstream commit 1eb70f54c445fcbb25817841e774adb3d912f3e8 ]

xfs_repair catches fork size/format mismatches, but the in-kernel
verifier doesn't, leading to null pointer failures when attempting
to perform operations on the fork. This can occur in the
xfs_dir_is_empty() where the in-memory fork format does not match
the size and so the fork data pointer is accessed incorrectly.

Note: this causes new failures in xfs/348 which is testing mode vs
ftype mismatches. We now detect a regular file that has been changed
to a directory or symlink mode as being corrupt because the data
fork is for a symlink or directory should be in local form when
there are only 3 bytes of data in the data fork. Hence the inode
verify for the regular file now fires w/ -EFSCORRUPTED because
the inode fork format does not match the format the corrupted mode
says it should be in.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/xfs/libxfs/xfs_inode_buf.c | 35 ++++++++++++++++++++++++++---------
1 file changed, 26 insertions(+), 9 deletions(-)

--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -337,19 +337,36 @@ xfs_dinode_verify_fork(
int whichfork)
{
uint32_t di_nextents = XFS_DFORK_NEXTENTS(dip, whichfork);
+ mode_t mode = be16_to_cpu(dip->di_mode);
+ uint32_t fork_size = XFS_DFORK_SIZE(dip, mp, whichfork);
+ uint32_t fork_format = XFS_DFORK_FORMAT(dip, whichfork);

- switch (XFS_DFORK_FORMAT(dip, whichfork)) {
+ /*
+ * For fork types that can contain local data, check that the fork
+ * format matches the size of local data contained within the fork.
+ *
+ * For all types, check that when the size says the should be in extent
+ * or btree format, the inode isn't claiming it is in local format.
+ */
+ if (whichfork == XFS_DATA_FORK) {
+ if (S_ISDIR(mode) || S_ISLNK(mode)) {
+ if (be64_to_cpu(dip->di_size) <= fork_size &&
+ fork_format != XFS_DINODE_FMT_LOCAL)
+ return __this_address;
+ }
+
+ if (be64_to_cpu(dip->di_size) > fork_size &&
+ fork_format == XFS_DINODE_FMT_LOCAL)
+ return __this_address;
+ }
+
+ switch (fork_format) {
case XFS_DINODE_FMT_LOCAL:
/*
- * no local regular files yet
+ * No local regular files yet.
*/
- if (whichfork == XFS_DATA_FORK) {
- if (S_ISREG(be16_to_cpu(dip->di_mode)))
- return __this_address;
- if (be64_to_cpu(dip->di_size) >
- XFS_DFORK_SIZE(dip, mp, whichfork))
- return __this_address;
- }
+ if (S_ISREG(mode) && whichfork == XFS_DATA_FORK)
+ return __this_address;
if (di_nextents)
return __this_address;
break;