From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C32C2C6369E for ; Thu, 3 Dec 2020 02:31:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DD3322249 for ; Thu, 3 Dec 2020 02:31:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726881AbgLCCbK (ORCPT ); Wed, 2 Dec 2020 21:31:10 -0500 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:34325 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725859AbgLCCbJ (ORCPT ); Wed, 2 Dec 2020 21:31:09 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R741e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0UHMxN9K_1606962624; Received: from B-D1K7ML85-0059.local(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0UHMxN9K_1606962624) by smtp.aliyun-inc.com(127.0.0.1); Thu, 03 Dec 2020 10:30:25 +0800 Subject: Re: [PATCH] io_uring: always let io_iopoll_complete() complete polled io. To: Xiaoguang Wang , io-uring@vger.kernel.org Cc: axboe@kernel.dk References: <20201202113151.1680-1-xiaoguang.wang@linux.alibaba.com> From: Joseph Qi Message-ID: <32e75a1d-4e53-e096-7368-9614174db1e5@linux.alibaba.com> Date: Thu, 3 Dec 2020 10:30:24 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201202113151.1680-1-xiaoguang.wang@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 12/2/20 7:31 PM, Xiaoguang Wang wrote: > Abaci Fuzz reported a double-free or invalid-free BUG in io_commit_cqring(): > [ 95.504842] BUG: KASAN: double-free or invalid-free in io_commit_cqring+0x3ec/0x8e0 > [ 95.505921] > [ 95.506225] CPU: 0 PID: 4037 Comm: io_wqe_worker-0 Tainted: G B > W 5.10.0-rc5+ #1 > [ 95.507434] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 > [ 95.508248] Call Trace: > [ 95.508683] dump_stack+0x107/0x163 > [ 95.509323] ? io_commit_cqring+0x3ec/0x8e0 > [ 95.509982] print_address_description.constprop.0+0x3e/0x60 > [ 95.510814] ? vprintk_func+0x98/0x140 > [ 95.511399] ? io_commit_cqring+0x3ec/0x8e0 > [ 95.512036] ? io_commit_cqring+0x3ec/0x8e0 > [ 95.512733] kasan_report_invalid_free+0x51/0x80 > [ 95.513431] ? io_commit_cqring+0x3ec/0x8e0 > [ 95.514047] __kasan_slab_free+0x141/0x160 > [ 95.514699] kfree+0xd1/0x390 > [ 95.515182] io_commit_cqring+0x3ec/0x8e0 > [ 95.515799] __io_req_complete.part.0+0x64/0x90 > [ 95.516483] io_wq_submit_work+0x1fa/0x260 > [ 95.517117] io_worker_handle_work+0xeac/0x1c00 > [ 95.517828] io_wqe_worker+0xc94/0x11a0 > [ 95.518438] ? io_worker_handle_work+0x1c00/0x1c00 > [ 95.519151] ? __kthread_parkme+0x11d/0x1d0 > [ 95.519806] ? io_worker_handle_work+0x1c00/0x1c00 > [ 95.520512] ? io_worker_handle_work+0x1c00/0x1c00 > [ 95.521211] kthread+0x396/0x470 > [ 95.521727] ? _raw_spin_unlock_irq+0x24/0x30 > [ 95.522380] ? kthread_mod_delayed_work+0x180/0x180 > [ 95.523108] ret_from_fork+0x22/0x30 > [ 95.523684] > [ 95.523985] Allocated by task 4035: > [ 95.524543] kasan_save_stack+0x1b/0x40 > [ 95.525136] __kasan_kmalloc.constprop.0+0xc2/0xd0 > [ 95.525882] kmem_cache_alloc_trace+0x17b/0x310 > [ 95.533930] io_queue_sqe+0x225/0xcb0 > [ 95.534505] io_submit_sqes+0x1768/0x25f0 > [ 95.535164] __x64_sys_io_uring_enter+0x89e/0xd10 > [ 95.535900] do_syscall_64+0x33/0x40 > [ 95.536465] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 95.537199] > [ 95.537505] Freed by task 4035: > [ 95.538003] kasan_save_stack+0x1b/0x40 > [ 95.538599] kasan_set_track+0x1c/0x30 > [ 95.539177] kasan_set_free_info+0x1b/0x30 > [ 95.539798] __kasan_slab_free+0x112/0x160 > [ 95.540427] kfree+0xd1/0x390 > [ 95.540910] io_commit_cqring+0x3ec/0x8e0 > [ 95.541516] io_iopoll_complete+0x914/0x1390 > [ 95.542150] io_do_iopoll+0x580/0x700 > [ 95.542724] io_iopoll_try_reap_events.part.0+0x108/0x200 > [ 95.543512] io_ring_ctx_wait_and_kill+0x118/0x340 > [ 95.544206] io_uring_release+0x43/0x50 > [ 95.544791] __fput+0x28d/0x940 > [ 95.545291] task_work_run+0xea/0x1b0 > [ 95.545873] do_exit+0xb6a/0x2c60 > [ 95.546400] do_group_exit+0x12a/0x320 > [ 95.546967] __x64_sys_exit_group+0x3f/0x50 > [ 95.547605] do_syscall_64+0x33/0x40 > [ 95.548155] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > The reason is that once we got a non EAGAIN error in io_wq_submit_work(), > we'll complete req by calling io_req_complete(), which will hold completion_lock > to call io_commit_cqring(), but for polled io, io_iopoll_complete() won't > hold completion_lock to call io_commit_cqring(), then there maybe concurrent > access to ctx->defer_list, double free may happen. > > To fix this bug, we always let io_iopoll_complete() complete polled io. > > Reported-by: Abaci Fuzz > Signed-off-by: Xiaoguang Wang > --- > fs/io_uring.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index a8c136a..901ca67 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -6074,8 +6074,19 @@ static struct io_wq_work *io_wq_submit_work(struct io_wq_work *work) > } > > if (ret) { > - req_set_fail_links(req); > - io_req_complete(req, ret); > + /* > + * io_iopoll_complete() does not hold completion_lock to complete > + * polled io, so here for polled io, just mark it done and still let > + * io_iopoll_complete() complete it. > + */ > + if (req->ctx->flags & IORING_SETUP_IOPOLL) { > + struct kiocb *kiocb = &req->rw.kiocb; > + > + kiocb_done(kiocb, ret, NULL); > + } else { > + req_set_fail_links(req); > + io_req_complete(req, ret); > + } > } > > return io_steal_work(req); > This patch can also fix another BUG I'm looking at: [ 61.359713] BUG: KASAN: double-free or invalid-free in io_dismantle_req+0x938/0xf40 ... [ 61.409315] refcount_t: underflow; use-after-free. [ 61.410261] WARNING: CPU: 1 PID: 1022 at lib/refcount.c:28 refcount_warn_saturate+0x266/0x2a0 ... It blames io_put_identity() has been called more than once and then identity->count is underflow. Reviewed-by: Joseph Qi