ext4: fix potential memory leak in ext4_fc_record_modified_inode()

As krealloc may return NULL, in this case 'state->fc_modified_inodes'
may not be freed by krealloc, but 'state->fc_modified_inodes' already
set NULL. Then will lead to 'state->fc_modified_inodes' memory leak.

Cc: stable@kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220921064040.3693255-2-yebin10@huawei.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/fast_commit.c

@@ -1486,13 +1486,15 @@ static int ext4_fc_record_modified_inode(struct super_block *sb, int ino)
 		if (state->fc_modified_inodes[i] == ino)
 			return 0;
 	if (state->fc_modified_inodes_used == state->fc_modified_inodes_size) {
-		state->fc_modified_inodes = krealloc(
-				state->fc_modified_inodes,
+		int *fc_modified_inodes;
+
+		fc_modified_inodes = krealloc(state->fc_modified_inodes,
 				sizeof(int) * (state->fc_modified_inodes_size +
 				EXT4_FC_REPLAY_REALLOC_INCREMENT),
 				GFP_KERNEL);
-		if (!state->fc_modified_inodes)
+		if (!fc_modified_inodes)
 			return -ENOMEM;
+		state->fc_modified_inodes = fc_modified_inodes;
 		state->fc_modified_inodes_size +=
 			EXT4_FC_REPLAY_REALLOC_INCREMENT;
 	}