[PATCH 6.6.y] kernel BUG in ocfs2_remove_extent

[driz2t@xxxxxx]

This is a backport for 6.6.y.

[ Upstream commit e1c70505ee8158c1108340d9cd67182ade93af4a ]

ocfs2: add extra consistency checks for chain allocator dinodes

When validating chain allocator dinode in 'ocfs2_validate_inode_block()',
add an extra checks whether a) the maximum amount of chain records in
'struct ocfs2_chain_list' matches the value calculated based on the
filesystem block size, and b) the next free slot index is within the valid
range.

Link: https://lkml.kernel.org/r/20251030153003.1934585-1-dmantipov@xxxxxxxxx
Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx>
Reported-by: syzbot+77026564530dbc29b854@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=77026564530dbc29b854
Reported-by: syzbot+5054473a31f78f735416@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=5054473a31f78f735416
Suggested-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Tested-by: syzbot+1dd53396e7124586dca9@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Changjian Liu <driz2t@xxxxxx>
---
 fs/ocfs2/inode.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index c561a8a6493e..7c99f436037b 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1419,6 +1419,23 @@ int ocfs2_validate_inode_block(struct super_block *sb,
            goto bail;
      }
 
+     if (le32_to_cpu(di->i_flags) & OCFS2_CHAIN_FL) {
+           struct ocfs2_chain_list *cl = &di->id2.i_chain;
+
+           if (le16_to_cpu(cl->cl_count) != ocfs2_chain_recs_per_inode(sb)) {
+                 rc = ocfs2_error(sb, "Invalid dinode %llu: chain list count %u\n",
+                              (unsigned long long)bh->b_blocknr,
+                              le16_to_cpu(cl->cl_count));
+                 goto bail;
+           }
+           if (le16_to_cpu(cl->cl_next_free_rec) > le16_to_cpu(cl->cl_count)) {
+                 rc = ocfs2_error(sb, "Invalid dinode %llu: chain list index %u\n",
+                              (unsigned long long)bh->b_blocknr,
+                              le16_to_cpu(cl->cl_next_free_rec));
+                 goto bail;
+           }
+     }
+
      rc = 0;
 
 bail:
--
2.43.0