[PATCH] ext4: xattr: fix null pointer deref in ext4_raw_inode()

[Karina Yankevich <k.yankevich@omp.ru>]

If ext4_get_inode_loc() fails (e.g. if it returns -EFSCORRUPTED),
iloc.bh will remain set to NULL. Since ext4_xattr_inode_dec_ref_all()
lacks error checking, this will lead to a null pointer dereference
in ext4_raw_inode(), called right after ext4_get_inode_loc().

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: c8e008b60492 ("ext4: ignore xattrs past end")
Signed-off-by: Karina Yankevich <k.yankevich@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
---
 fs/ext4/xattr.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index ce7253b3f549..2e02efbddaac 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1174,7 +1174,11 @@ ext4_xattr_inode_dec_ref_all(handle_t *handle, struct inode *parent,
 	if (block_csum)
 		end = (void *)bh->b_data + bh->b_size;
 	else {
-		ext4_get_inode_loc(parent, &iloc);
+		err = ext4_get_inode_loc(parent, &iloc);
+		if (err) {
+			EXT4_ERROR_INODE(parent, "parent inode loc (error %d)", err);
+			return;
+		}
 		end = (void *)ext4_raw_inode(&iloc) + EXT4_SB(parent->i_sb)->s_inode_size;
 	}
 
-- 
2.34.1