io_uring: convert params to pointer in ring reisze

The parameters in io_register_resize_rings() will be moved into another
structure in a later patch. In preparation to that, convert the params
variable it to a pointer, but still store the data on stack.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/register.c

@@ -402,33 +402,33 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	struct io_ring_ctx_rings o = { }, n = { }, *to_free = NULL;
 	size_t size, sq_array_offset;
 	unsigned i, tail, old_head;
-	struct io_uring_params p;
+	struct io_uring_params __p, *p = &__p;
 	int ret;
 
 	/* limited to DEFER_TASKRUN for now */
 	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN))
 		return -EINVAL;
-	if (copy_from_user(&p, arg, sizeof(p)))
+	if (copy_from_user(p, arg, sizeof(*p)))
 		return -EFAULT;
-	if (p.flags & ~RESIZE_FLAGS)
+	if (p->flags & ~RESIZE_FLAGS)
 		return -EINVAL;
 
 	/* properties that are always inherited */
-	p.flags |= (ctx->flags & COPY_FLAGS);
+	p->flags |= (ctx->flags & COPY_FLAGS);
 
-	ret = io_uring_fill_params(&p);
+	ret = io_uring_fill_params(p);
 	if (unlikely(ret))
 		return ret;
 
-	size = rings_size(p.flags, p.sq_entries, p.cq_entries,
+	size = rings_size(p->flags, p->sq_entries, p->cq_entries,
 				&sq_array_offset);
 	if (size == SIZE_MAX)
 		return -EOVERFLOW;
 
 	memset(&rd, 0, sizeof(rd));
 	rd.size = PAGE_ALIGN(size);
-	if (p.flags & IORING_SETUP_NO_MMAP) {
-		rd.user_addr = p.cq_off.user_addr;
+	if (p->flags & IORING_SETUP_NO_MMAP) {
+		rd.user_addr = p->cq_off.user_addr;
 		rd.flags |= IORING_MEM_REGION_TYPE_USER;
 	}
 	ret = io_create_region(ctx, &n.ring_region, &rd, IORING_OFF_CQ_RING);
@@ -445,29 +445,29 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	 * intent... Use read/write once helpers from here on to indicate the
 	 * shared nature of it.
 	 */
-	WRITE_ONCE(n.rings->sq_ring_mask, p.sq_entries - 1);
-	WRITE_ONCE(n.rings->cq_ring_mask, p.cq_entries - 1);
-	WRITE_ONCE(n.rings->sq_ring_entries, p.sq_entries);
-	WRITE_ONCE(n.rings->cq_ring_entries, p.cq_entries);
+	WRITE_ONCE(n.rings->sq_ring_mask, p->sq_entries - 1);
+	WRITE_ONCE(n.rings->cq_ring_mask, p->cq_entries - 1);
+	WRITE_ONCE(n.rings->sq_ring_entries, p->sq_entries);
+	WRITE_ONCE(n.rings->cq_ring_entries, p->cq_entries);
 
-	if (copy_to_user(arg, &p, sizeof(p))) {
+	if (copy_to_user(arg, p, sizeof(*p))) {
 		io_register_free_rings(ctx, &n);
 		return -EFAULT;
 	}
 
-	if (p.flags & IORING_SETUP_SQE128)
-		size = array_size(2 * sizeof(struct io_uring_sqe), p.sq_entries);
+	if (p->flags & IORING_SETUP_SQE128)
+		size = array_size(2 * sizeof(struct io_uring_sqe), p->sq_entries);
 	else
-		size = array_size(sizeof(struct io_uring_sqe), p.sq_entries);
+		size = array_size(sizeof(struct io_uring_sqe), p->sq_entries);
 	if (size == SIZE_MAX) {
 		io_register_free_rings(ctx, &n);
 		return -EOVERFLOW;
 	}
 
 	memset(&rd, 0, sizeof(rd));
 	rd.size = PAGE_ALIGN(size);
-	if (p.flags & IORING_SETUP_NO_MMAP) {
-		rd.user_addr = p.sq_off.user_addr;
+	if (p->flags & IORING_SETUP_NO_MMAP) {
+		rd.user_addr = p->sq_off.user_addr;
 		rd.flags |= IORING_MEM_REGION_TYPE_USER;
 	}
 	ret = io_create_region(ctx, &n.sq_region, &rd, IORING_OFF_SQES);
@@ -508,11 +508,11 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	 */
 	tail = READ_ONCE(o.rings->sq.tail);
 	old_head = READ_ONCE(o.rings->sq.head);
-	if (tail - old_head > p.sq_entries)
+	if (tail - old_head > p->sq_entries)
 		goto overflow;
 	for (i = old_head; i < tail; i++) {
 		unsigned src_head = i & (ctx->sq_entries - 1);
-		unsigned dst_head = i & (p.sq_entries - 1);
+		unsigned dst_head = i & (p->sq_entries - 1);
 
 		n.sq_sqes[dst_head] = o.sq_sqes[src_head];
 	}
@@ -521,7 +521,7 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 
 	tail = READ_ONCE(o.rings->cq.tail);
 	old_head = READ_ONCE(o.rings->cq.head);
-	if (tail - old_head > p.cq_entries) {
+	if (tail - old_head > p->cq_entries) {
 overflow:
 		/* restore old rings, and return -EOVERFLOW via cleanup path */
 		ctx->rings = o.rings;
@@ -532,7 +532,7 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	}
 	for (i = old_head; i < tail; i++) {
 		unsigned src_head = i & (ctx->cq_entries - 1);
-		unsigned dst_head = i & (p.cq_entries - 1);
+		unsigned dst_head = i & (p->cq_entries - 1);
 
 		n.rings->cqes[dst_head] = o.rings->cqes[src_head];
 	}
@@ -550,8 +550,8 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	if (!(ctx->flags & IORING_SETUP_NO_SQARRAY))
 		ctx->sq_array = (u32 *)((char *)n.rings + sq_array_offset);
 
-	ctx->sq_entries = p.sq_entries;
-	ctx->cq_entries = p.cq_entries;
+	ctx->sq_entries = p->sq_entries;
+	ctx->cq_entries = p->cq_entries;
 
 	ctx->rings = n.rings;
 	ctx->sq_sqes = n.sq_sqes;