[PATCH] ocfs2: fix NULL pointer dereference in ocfs2_xattr_get_rec

[Jiasheng Jiang]

In ocfs2_xattr_get_rec, the variable 'rec' is initialized to NULL.
If the extent list 'el' is empty (l_next_free_rec == 0), the loop
iterating over the records is skipped, leaving 'rec' as NULL.

Since 'e_blkno' is initialized to 0, the function enters the error
handling block 'if (!e_blkno)'. Inside this block, the function calls
ocfs2_error() and attempts to dereference 'rec' via
'le32_to_cpu(rec->e_cpos)' and 'ocfs2_rec_clusters(el, rec)'. This
results in a NULL pointer dereference and a kernel panic.

Fix this by ensuring 'rec' is not NULL before accessing its members
within the error handling path, or by checking for an empty list
explicitly.

Signed-off-by: Jiasheng Jiang <jiashengjiangcool@xxxxxxxxx>
---
 fs/ocfs2/xattr.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 1b21fbc16d73..b018c84dbc05 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -3757,10 +3757,16 @@ static int ocfs2_xattr_get_rec(struct inode *inode,
 	}
 
 	if (!e_blkno) {
-		ret = ocfs2_error(inode->i_sb, "Inode %lu has bad extent record (%u, %u, 0) in xattr\n",
-				  inode->i_ino,
-				  le32_to_cpu(rec->e_cpos),
-				  ocfs2_rec_clusters(el, rec));
+		if (rec)
+			ret = ocfs2_error(inode->i_sb,
+					  "Inode %lu has bad extent record (%u, %u, 0) in xattr\n",
+					  inode->i_ino,
+					  le32_to_cpu(rec->e_cpos),
+					  ocfs2_rec_clusters(el, rec));
+		else
+			ret = ocfs2_error(inode->i_sb,
+					  "Inode %lu has bad extent record (NULL) in xattr\n",
+					  inode->i_ino);
 		goto out;
 	}
 
-- 
2.25.1