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Subject[PATCH 2/2] io_uring: Add KASAN support for alloc_caches
Date
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>
---
io_uring/alloc_cache.h | 11 ++++++++---
io_uring/io_uring.c | 12 ++++++++++--
io_uring/net.c | 2 +-
io_uring/poll.c | 2 +-
4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/io_uring/alloc_cache.h b/io_uring/alloc_cache.h
index 0d9ff9402a37..0d5cd2c0a0ba 100644
--- a/io_uring/alloc_cache.h
+++ b/io_uring/alloc_cache.h
@@ -16,12 +16,15 @@ 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;
@@ -29,6 +32,7 @@ static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *c
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);
}

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 80b6204769e8..6a98902b8f62 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2766,6 +2766,15 @@ 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);
@@ -2781,8 +2790,7 @@ 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)
diff --git a/io_uring/net.c b/io_uring/net.c
index fbc34a7c2743..8dc67b23b030 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -139,7 +139,7 @@ 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;
diff --git a/io_uring/poll.c b/io_uring/poll.c
index 8339a92b4510..295d59875f00 100644
--- a/io_uring/poll.c
+++ b/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);
--
2.39.0
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