io_uring: Fix premature return from loop and memory leak

Currently the -EINVAL error return path is leaking memory allocated
to data. Fix this by not returning immediately but instead setting
the error return variable to -EINVAL and breaking out of the loop.

Kudos to Pavel Begunkov for suggesting a correct fix.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/20210429104602.62676-1-colin.king@canonical.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Colin Ian King

fs/io_uring.c

@@ -8417,8 +8417,10 @@ static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 		ret = io_buffer_validate(&iov);
 		if (ret)
 			break;
-		if (!iov.iov_base && tag)
-			return -EINVAL;
+		if (!iov.iov_base && tag) {
+			ret = -EINVAL;
+			break;
+		}
 
 		ret = io_sqe_buffer_register(ctx, &iov, &ctx->user_bufs[i],
 					     &last_hpage);
@@ -8468,8 +8470,10 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
 		err = io_buffer_validate(&iov);
 		if (err)
 			break;
-		if (!iov.iov_base && tag)
-			return -EINVAL;
+		if (!iov.iov_base && tag) {
+			err = -EINVAL;
+			break;
+		}
 		err = io_sqe_buffer_register(ctx, &iov, &imu, &last_hpage);
 		if (err)
 			break;