io_uring: Add KASAN support for alloc_caches

Add support for KASAN in the alloc_caches (apoll and netmsg_cache).
Thus, if something touches the unused caches, it will raise a KASAN
warning/exception.

It poisons the object when the object is put to the cache, and unpoisons
it when the object is gotten or freed.

Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20230221135721.3230763-2-leitao@debian.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/alloc_cache.h

@@ -16,19 +16,23 @@ static inline bool io_alloc_cache_put(struct io_alloc_cache *cache,
 	if (cache->nr_cached < IO_ALLOC_CACHE_MAX) {
 		cache->nr_cached++;
 		wq_stack_add_head(&entry->node, &cache->list);
+		/* KASAN poisons object */
+		kasan_slab_free_mempool(entry);
 		return true;
 	}
 	return false;
 }
 
-static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *cache)
+static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *cache,
+							size_t size)
 {
 	struct io_wq_work_node *node;
 	struct io_cache_entry *entry;
 
 	if (cache->list.next) {
 		node = cache->list.next;
 		entry = container_of(node, struct io_cache_entry, node);
+		kasan_unpoison_range(entry, size);
 		cache->list.next = node->next;
 		return entry;
 	}
@@ -43,11 +47,12 @@ static inline void io_alloc_cache_init(struct io_alloc_cache *cache)
 }
 
 static inline void io_alloc_cache_free(struct io_alloc_cache *cache,
-					void (*free)(struct io_cache_entry *))
+					void (*free)(struct io_cache_entry *),
+					size_t size)
 {
 	struct io_cache_entry *entry;
 
-	while ((entry = io_alloc_cache_get(cache))) {
+	while ((entry = io_alloc_cache_get(cache, size))) {
 		free(entry);
 	}
 

io_uring/io_uring.c

@@ -2772,6 +2772,15 @@ static void io_req_caches_free(struct io_ring_ctx *ctx)
 	mutex_unlock(&ctx->uring_lock);
 }
 
+static __cold void io_uring_acache_free(struct io_ring_ctx *ctx)
+{
+
+	io_alloc_cache_free(&ctx->apoll_cache, io_apoll_cache_free,
+			    sizeof(struct async_poll));
+	io_alloc_cache_free(&ctx->netmsg_cache, io_netmsg_cache_free,
+			    sizeof(struct io_async_msghdr));
+}
+
 static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 {
 	io_sq_thread_finish(ctx);
@@ -2787,8 +2796,7 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 		__io_sqe_files_unregister(ctx);
 	io_cqring_overflow_kill(ctx);
 	io_eventfd_unregister(ctx);
-	io_alloc_cache_free(&ctx->apoll_cache, io_apoll_cache_free);
-	io_alloc_cache_free(&ctx->netmsg_cache, io_netmsg_cache_free);
+	io_uring_acache_free(ctx);
 	mutex_unlock(&ctx->uring_lock);
 	io_destroy_buffers(ctx);
 	if (ctx->sq_creds)

io_uring/net.c

@@ -140,7 +140,7 @@ static struct io_async_msghdr *io_msg_alloc_async(struct io_kiocb *req,
 	struct io_async_msghdr *hdr;
 
 	if (!(issue_flags & IO_URING_F_UNLOCKED)) {
-		entry = io_alloc_cache_get(&ctx->netmsg_cache);
+		entry = io_alloc_cache_get(&ctx->netmsg_cache, sizeof(struct io_async_msghdr));
 		if (entry) {
 			hdr = container_of(entry, struct io_async_msghdr, cache);
 			hdr->free_iov = NULL;

io_uring/poll.c

@@ -661,7 +661,7 @@ static struct async_poll *io_req_alloc_apoll(struct io_kiocb *req,
 		apoll = req->apoll;
 		kfree(apoll->double_poll);
 	} else if (!(issue_flags & IO_URING_F_UNLOCKED)) {
-		entry = io_alloc_cache_get(&ctx->apoll_cache);
+		entry = io_alloc_cache_get(&ctx->apoll_cache, sizeof(struct async_poll));
 		if (entry == NULL)
 			goto alloc_apoll;
 		apoll = container_of(entry, struct async_poll, cache);