From ff6aea290450f00e084cafe5b34901d26abdbc4a Mon Sep 17 00:00:00 2001
From: Dave Chinner <dchinner@redhat.com>
Date: Wed, 22 Jun 2022 14:28:52 -0500
Subject: [PATCH] xfs: validate inode fork size against fork format

Source kernel 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: Eric Sandeen <sandeen@sandeen.net>
---
 libxfs/xfs_inode_buf.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/libxfs/xfs_inode_buf.c b/libxfs/xfs_inode_buf.c
index f98f5c4..7ecbfad 100644
--- a/libxfs/xfs_inode_buf.c
+++ b/libxfs/xfs_inode_buf.c
@@ -334,19 +334,36 @@ 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;
-- 
1.8.3.1

