ext4: fix some error pointer dereferences

We can't pass error pointers to brelse().

Fixes: fb265c9 ("ext4: add ext4_sb_bread() to disambiguate ENOMEM cases")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

fs/ext4/xattr.c

@@ -829,6 +829,7 @@ int ext4_get_inode_usage(struct inode *inode, qsize_t *usage)
 		bh = ext4_sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
 		if (IS_ERR(bh)) {
 			ret = PTR_ERR(bh);
+			bh = NULL;
 			goto out;
 		}
 
@@ -2903,6 +2904,7 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
 			if (error == -EIO)
 				EXT4_ERROR_INODE(inode, "block %llu read error",
 						 EXT4_I(inode)->i_file_acl);
+			bh = NULL;
 			goto cleanup;
 		}
 		error = ext4_xattr_check_block(inode, bh);
@@ -3059,6 +3061,7 @@ ext4_xattr_block_cache_find(struct inode *inode,
 		if (IS_ERR(bh)) {
 			if (PTR_ERR(bh) == -ENOMEM)
 				return NULL;
+			bh = NULL;
 			EXT4_ERROR_INODE(inode, "block %lu read error",
 					 (unsigned long)ce->e_value);
 		} else if (ext4_xattr_cmp(header, BHDR(bh)) == 0) {