io_uring/rsrc: clean up __io_sqe_buffers_update()

Inline offset variable, so we don't use it without subjecting it to
array_index_nospec() first.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/77936d9ed23755588810c5eafcea7e1c3b90e3cd.1681395792.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/rsrc.c

@@ -469,7 +469,6 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
 
 	for (done = 0; done < nr_args; done++) {
 		struct io_mapped_ubuf *imu;
-		int offset = up->offset + done;
 		u64 tag = 0;
 
 		err = io_copy_iov(ctx, &iov, iovs, done);
@@ -490,7 +489,7 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
 		if (err)
 			break;
 
-		i = array_index_nospec(offset, ctx->nr_user_bufs);
+		i = array_index_nospec(up->offset + done, ctx->nr_user_bufs);
 		if (ctx->user_bufs[i] != ctx->dummy_ubuf) {
 			err = io_queue_rsrc_removal(ctx->buf_data, i,
 						    ctx->rsrc_node, ctx->user_bufs[i]);