io_uring: Enable KASAN for request cache

Every io_uring request is represented by struct io_kiocb, which is
cached locally by io_uring (not SLAB/SLUB) in the list called
submit_state.freelist. This patch simply enabled KASAN for this free
list.

This list is initially created by KMEM_CACHE, but later, managed by
io_uring. This patch basically poisons the objects that are not used
(i.e., they are the free list), and unpoisons it when the object is
allocated/removed from the list.

Touching these poisoned objects while in the freelist will cause a KASAN
warning.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index c84dce6944db94a4fd586ba8143782dee9cf33a5..407834255a592fd38e779d85714fad851140e34e 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -151,7 +151,7 @@ static void io_move_task_work_from_local(struct io_ring_ctx *ctx);
 static void __io_submit_flush_completions(struct io_ring_ctx *ctx);
 static __cold void io_fallback_tw(struct io_uring_task *tctx);
 
-static struct kmem_cache *req_cachep;
+struct kmem_cache *req_cachep;
 
 struct sock *io_uring_get_socket(struct file *file)
 {
@@ -230,6 +230,7 @@ static inline void req_fail_link_node(struct io_kiocb *req, int res)
 static inline void io_req_add_to_cache(struct io_kiocb *req, struct io_ring_ctx *ctx)
 {
        wq_stack_add_head(&req->comp_list, &ctx->submit_state.free_list);
+       kasan_poison_object_data(req_cachep, req);
 }
 
 static __cold void io_ring_ctx_ref_free(struct percpu_ref *ref)

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index d58cfe062da90b522cc3d3b0038c3c47f313143d..9270156288aade58db3963477cab9020c5a64699 100644 (file)
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -4,6 +4,7 @@
 #include <linux/errno.h>
 #include <linux/lockdep.h>
 #include <linux/resume_user_mode.h>
+#include <linux/kasan.h>
 #include <linux/io_uring_types.h>
 #include <uapi/linux/eventpoll.h>
 #include "io-wq.h"
@@ -347,12 +348,16 @@ static inline bool io_alloc_req_refill(struct io_ring_ctx *ctx)
        return true;
 }
 
+extern struct kmem_cache *req_cachep;
+
 static inline struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
 {
-       struct io_wq_work_node *node;
+       struct io_kiocb *req;
 
-       node = wq_stack_extract(&ctx->submit_state.free_list);
-       return container_of(node, struct io_kiocb, comp_list);
+       req = container_of(ctx->submit_state.free_list.next, struct io_kiocb, comp_list);
+       kasan_unpoison_object_data(req_cachep, req);
+       wq_stack_extract(&ctx->submit_state.free_list);
+       return req;
 }
 
 static inline bool io_allowed_defer_tw_run(struct io_ring_ctx *ctx)