From: Al Viro Date: Thu, 24 May 2018 02:53:22 +0000 (-0400) Subject: fix io_destroy()/aio_complete() race X-Git-Tag: v4.19~764^2~3 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=4faa99965e027cc057c5145ce45fa772caa04e8d;p=platform%2Fkernel%2Flinux-rpi.git fix io_destroy()/aio_complete() race If io_destroy() gets to cancelling everything that can be cancelled and gets to kiocb_cancel() calling the function driver has left in ->ki_cancel, it becomes vulnerable to a race with IO completion. At that point req is already taken off the list and aio_complete() does *NOT* spin until we (in free_ioctx_users()) releases ->ctx_lock. As the result, it proceeds to kiocb_free(), freing req just it gets passed to ->ki_cancel(). Fix is simple - remove from the list after the call of kiocb_cancel(). All instances of ->ki_cancel() already have to cope with the being called with iocb still on list - that's what happens in io_cancel(2). Cc: stable@kernel.org Fixes: 0460fef2a921 "aio: use cancellation list lazily" Signed-off-by: Al Viro --- diff --git a/fs/aio.c b/fs/aio.c index 8061d97..49f5351 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -634,9 +634,8 @@ static void free_ioctx_users(struct percpu_ref *ref) while (!list_empty(&ctx->active_reqs)) { req = list_first_entry(&ctx->active_reqs, struct aio_kiocb, ki_list); - - list_del_init(&req->ki_list); kiocb_cancel(req); + list_del_init(&req->ki_list); } spin_unlock_irq(&ctx->ctx_lock);