[PATCH 6.18.y 2/3] ocfs2: validate inline data i_size during inode read

[Sasha Levin <sashal@kernel.org>]

From: Deepanshu Kartikey <kartikey406@gmail.com>

[ Upstream commit 1524af3685b35feac76662cc551cbc37bd14775f ]

When reading an inode from disk, ocfs2_validate_inode_block() performs
various sanity checks but does not validate the size of inline data.  If
the filesystem is corrupted, an inode's i_size can exceed the actual
inline data capacity (id_count).

This causes ocfs2_dir_foreach_blk_id() to iterate beyond the inline data
buffer, triggering a use-after-free when accessing directory entries from
freed memory.

In the syzbot report:
  - i_size was 1099511627576 bytes (~1TB)
  - Actual inline data capacity (id_count) is typically <256 bytes
  - A garbage rec_len (54648) caused ctx->pos to jump out of bounds
  - This triggered a UAF in ocfs2_check_dir_entry()

Fix by adding a validation check in ocfs2_validate_inode_block() to ensure
inodes with inline data have i_size <= id_count.  This catches the
corruption early during inode read and prevents all downstream code from
operating on invalid data.

Link: https://lkml.kernel.org/r/20251212052132.16750-1-kartikey406@gmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Reported-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
Tested-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/20251211115231.3560028-1-kartikey406@gmail.com/T/ [v1]
Link: https://lore.kernel.org/all/20251212040400.6377-1-kartikey406@gmail.com/T/ [v2]
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 7bc5da4842be ("ocfs2: fix out-of-bounds write in ocfs2_write_end_inline")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ocfs2/inode.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index ef17f1bc741ef..e7d130f024f91 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1505,12 +1505,25 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		goto bail;
 	}
 
-	if ((le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) &&
-	    le32_to_cpu(di->i_clusters)) {
-		rc = ocfs2_error(sb, "Invalid dinode %llu: %u clusters\n",
-				 (unsigned long long)bh->b_blocknr,
-				 le32_to_cpu(di->i_clusters));
-		goto bail;
+	if (le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) {
+		struct ocfs2_inline_data *data = &di->id2.i_data;
+
+		if (le32_to_cpu(di->i_clusters)) {
+			rc = ocfs2_error(sb,
+					 "Invalid dinode %llu: %u clusters\n",
+					 (unsigned long long)bh->b_blocknr,
+					 le32_to_cpu(di->i_clusters));
+			goto bail;
+		}
+
+		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
+			rc = ocfs2_error(sb,
+					 "Invalid dinode #%llu: inline data i_size %llu exceeds id_count %u\n",
+					 (unsigned long long)bh->b_blocknr,
+					 (unsigned long long)le64_to_cpu(di->i_size),
+					 le16_to_cpu(data->id_count));
+			goto bail;
+		}
 	}
 
 	rc = 0;
-- 
2.53.0