Merge tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 fixes from Ted Ts'o:
 "Two more bug fixes (including a regression) for 5.6"

* tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  ext4: potential crash on allocation error in ext4_alloc_flex_bg_array()
  jbd2: fix data races at struct journal_head

fs/ext4/super.c

@@ -2391,7 +2391,7 @@ int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct flex_groups **old_groups, **new_groups;
-	int size, i;
+	int size, i, j;
 
 	if (!sbi->s_log_groups_per_flex)
 		return 0;
@@ -2412,8 +2412,8 @@ int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup)
 					 sizeof(struct flex_groups)),
 					 GFP_KERNEL);
 		if (!new_groups[i]) {
-			for (i--; i >= sbi->s_flex_groups_allocated; i--)
-				kvfree(new_groups[i]);
+			for (j = sbi->s_flex_groups_allocated; j < i; j++)
+				kvfree(new_groups[j]);
 			kvfree(new_groups);
 			ext4_msg(sb, KERN_ERR,
 				 "not enough memory for %d flex groups", size);

fs/jbd2/transaction.c

@@ -1150,8 +1150,8 @@ static bool jbd2_write_access_granted(handle_t *handle, struct buffer_head *bh,
 	/* For undo access buffer must have data copied */
 	if (undo && !jh->b_committed_data)
 		goto out;
-	if (jh->b_transaction != handle->h_transaction &&
-	    jh->b_next_transaction != handle->h_transaction)
+	if (READ_ONCE(jh->b_transaction) != handle->h_transaction &&
+	    READ_ONCE(jh->b_next_transaction) != handle->h_transaction)
 		goto out;
 	/*
 	 * There are two reasons for the barrier here:
@@ -2569,8 +2569,8 @@ bool __jbd2_journal_refile_buffer(struct journal_head *jh)
 	 * our jh reference and thus __jbd2_journal_file_buffer() must not
 	 * take a new one.
 	 */
-	jh->b_transaction = jh->b_next_transaction;
-	jh->b_next_transaction = NULL;
+	WRITE_ONCE(jh->b_transaction, jh->b_next_transaction);
+	WRITE_ONCE(jh->b_next_transaction, NULL);
 	if (buffer_freed(bh))
 		jlist = BJ_Forget;
 	else if (jh->b_modified)