linux-kernel - [PATCH v3 2/2] io_uring: Add KASAN support for alloc

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Date:   Thu, 23 Feb 2023 08:43:53 -0800
From:   Breno Leitao <leitao@...ian.org>
To:     axboe@...nel.dk, asml.silence@...il.com, io-uring@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, gustavold@...a.com, leit@...a.com,
        kasan-dev@...glegroups.com
Subject: [PATCH v3 2/2] 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@...ian.org>
---
 include/linux/io_uring_types.h | 1 +
 io_uring/alloc_cache.h         | 6 +++++-
 io_uring/io_uring.c            | 4 ++--
 io_uring/net.h                 | 5 ++++-
 4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index efa66b6c32c9..35ebcfb46047 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -190,6 +190,7 @@ struct io_ev_fd {
 struct io_alloc_cache {
 	struct io_wq_work_node	list;
 	unsigned int		nr_cached;
+	size_t			elem_size;
 };
 
 struct io_ring_ctx {
diff --git a/io_uring/alloc_cache.h b/io_uring/alloc_cache.h
index 301855e94309..3aba7b356320 100644
--- a/io_uring/alloc_cache.h
+++ b/io_uring/alloc_cache.h
@@ -16,6 +16,8 @@ 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;
@@ -27,6 +29,7 @@ static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *c
 		struct io_cache_entry *entry;
 
 		entry = container_of(cache->list.next, struct io_cache_entry, node);
+		kasan_unpoison_range(entry, cache->elem_size);
 		cache->list.next = cache->list.next->next;
 		return entry;
 	}
@@ -34,10 +37,11 @@ static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *c
 	return NULL;
 }
 
-static inline void io_alloc_cache_init(struct io_alloc_cache *cache)
+static inline void io_alloc_cache_init(struct io_alloc_cache *cache, size_t size)
 {
 	cache->list.next = NULL;
 	cache->nr_cached = 0;
+	cache->elem_size = size;
 }
 
 static inline void io_alloc_cache_free(struct io_alloc_cache *cache,
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 80b6204769e8..7a30a3e72fcc 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -309,8 +309,8 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	INIT_LIST_HEAD(&ctx->sqd_list);
 	INIT_LIST_HEAD(&ctx->cq_overflow_list);
 	INIT_LIST_HEAD(&ctx->io_buffers_cache);
-	io_alloc_cache_init(&ctx->apoll_cache);
-	io_alloc_cache_init(&ctx->netmsg_cache);
+	io_alloc_cache_init(&ctx->apoll_cache, sizeof(struct async_poll));
+	io_alloc_cache_init(&ctx->netmsg_cache, sizeof(struct io_async_msghdr));
 	init_completion(&ctx->ref_comp);
 	xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
 	mutex_init(&ctx->uring_lock);
diff --git a/io_uring/net.h b/io_uring/net.h
index 5ffa11bf5d2e..191009979bcb 100644
--- a/io_uring/net.h
+++ b/io_uring/net.h
@@ -5,8 +5,8 @@
 
 #include "alloc_cache.h"
 
-#if defined(CONFIG_NET)
 struct io_async_msghdr {
+#if defined(CONFIG_NET)
 	union {
 		struct iovec		fast_iov[UIO_FASTIOV];
 		struct {
@@ -22,8 +22,11 @@ struct io_async_msghdr {
 	struct sockaddr __user		*uaddr;
 	struct msghdr			msg;
 	struct sockaddr_storage		addr;
+#endif
 };
 
+#if defined(CONFIG_NET)
+
 struct io_async_connect {
 	struct sockaddr_storage		address;
 };
-- 
2.30.2