io_uring: introduce struct io_ctx_config

There will be more information needed during ctx setup, and instead of
passing a handful of pointers around, wrap them all into a new
structure. Add a helper for encapsulating all configuration checks and
preparation, that's also reused for ring resizing.

Note, it indirectly adds a io_uring_sanitise_params() check to ring
resizing, which is a good thing.

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

Author: isilence

io_uring/io_uring.c

@@ -3480,7 +3480,7 @@ static int io_uring_sanitise_params(struct io_uring_params *p)
 	return 0;
 }
 
-int io_uring_fill_params(struct io_uring_params *p)
+static int io_uring_fill_params(struct io_uring_params *p)
 {
 	unsigned entries = p->sq_entries;
 
@@ -3545,20 +3545,32 @@ int io_uring_fill_params(struct io_uring_params *p)
 	return 0;
 }
 
-static __cold int io_uring_create(struct io_uring_params *p,
-				  struct io_uring_params __user *params)
+int io_prepare_config(struct io_ctx_config *config)
 {
-	struct io_ring_ctx *ctx;
-	struct io_uring_task *tctx;
-	struct file *file;
+	struct io_uring_params *p = &config->p;
 	int ret;
 
 	ret = io_uring_sanitise_params(p);
 	if (ret)
 		return ret;
 
 	ret = io_uring_fill_params(p);
-	if (unlikely(ret))
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static __cold int io_uring_create(struct io_ctx_config *config)
+{
+	struct io_uring_params *p = &config->p;
+	struct io_ring_ctx *ctx;
+	struct io_uring_task *tctx;
+	struct file *file;
+	int ret;
+
+	ret = io_prepare_config(config);
+	if (ret)
 		return ret;
 
 	ctx = io_ring_ctx_alloc(p);
@@ -3631,7 +3643,7 @@ static __cold int io_uring_create(struct io_uring_params *p,
 
 	p->features = IORING_FEAT_FLAGS;
 
-	if (copy_to_user(params, p, sizeof(*p))) {
+	if (copy_to_user(config->uptr, p, sizeof(*p))) {
 		ret = -EFAULT;
 		goto err;
 	}
@@ -3684,16 +3696,19 @@ static __cold int io_uring_create(struct io_uring_params *p,
  */
 static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
 {
-	struct io_uring_params p;
+	struct io_ctx_config config;
+
+	memset(&config, 0, sizeof(config));
 
-	if (copy_from_user(&p, params, sizeof(p)))
+	if (copy_from_user(&config.p, params, sizeof(config.p)))
 		return -EFAULT;
 
-	if (!mem_is_zero(&p.resv, sizeof(p.resv)))
+	if (!mem_is_zero(&config.p.resv, sizeof(config.p.resv)))
 		return -EINVAL;
 
-	p.sq_entries = entries;
-	return io_uring_create(&p, params);
+	config.p.sq_entries = entries;
+	config.uptr = params;
+	return io_uring_create(&config);
 }
 
 static inline int io_uring_allowed(void)

io_uring/io_uring.h

@@ -17,6 +17,11 @@
 #include <trace/events/io_uring.h>
 #endif
 
+struct io_ctx_config {
+	struct io_uring_params p;
+	struct io_uring_params __user *uptr;
+};
+
 #define IORING_FEAT_FLAGS (IORING_FEAT_SINGLE_MMAP |\
 			IORING_FEAT_NODROP |\
 			IORING_FEAT_SUBMIT_STABLE |\
@@ -136,7 +141,8 @@ static inline bool io_should_wake(struct io_wait_queue *iowq)
 
 unsigned long rings_size(unsigned int flags, unsigned int sq_entries,
 			 unsigned int cq_entries, size_t *sq_offset);
-int io_uring_fill_params(struct io_uring_params *p);
+int io_prepare_config(struct io_ctx_config *config);
+
 bool io_cqe_cache_refill(struct io_ring_ctx *ctx, bool overflow, bool cqe32);
 int io_run_task_work_sig(struct io_ring_ctx *ctx);
 int io_run_local_work(struct io_ring_ctx *ctx, int min_events, int max_events);

io_uring/register.c

@@ -398,13 +398,16 @@ static void io_register_free_rings(struct io_ring_ctx *ctx,
 
 static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 {
+	struct io_ctx_config config;
 	struct io_uring_region_desc rd;
 	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, *p = &__p;
+	struct io_uring_params *p = &config.p;
 	int ret;
 
+	memset(&config, 0, sizeof(config));
+
 	/* limited to DEFER_TASKRUN for now */
 	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN))
 		return -EINVAL;
@@ -416,7 +419,7 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	/* properties that are always inherited */
 	p->flags |= (ctx->flags & COPY_FLAGS);
 
-	ret = io_uring_fill_params(p);
+	ret = io_prepare_config(&config);
 	if (unlikely(ret))
 		return ret;