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Tue, 26 Jan 2021 08:00:00 -0800 (PST) Subject: Re: [PATCH 2/2] io_uring: fix cancellation taking mutex while TASK_UNINTERRUPTIBLE From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org Cc: stable@vger.kernel.org, syzbot+f655445043a26a7cfab8@syzkaller.appspotmail.com References: <70fb7f91ecc0aeff3427c215ec7f46ceb77f88ef.1611674535.git.asml.silence@gmail.com> Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <5955c0cc-b671-9470-fe31-e4450e9c9c9a@gmail.com> Date: Tue, 26 Jan 2021 15:56:19 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <70fb7f91ecc0aeff3427c215ec7f46ceb77f88ef.1611674535.git.asml.silence@gmail.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 26/01/2021 15:28, Pavel Begunkov wrote: > do not call blocking ops when !TASK_RUNNING; state=2 set at > [<00000000ced9dbfc>] prepare_to_wait+0x1f4/0x3b0 > kernel/sched/wait.c:262 > WARNING: CPU: 1 PID: 19888 at kernel/sched/core.c:7853 > __might_sleep+0xed/0x100 kernel/sched/core.c:7848 > RIP: 0010:__might_sleep+0xed/0x100 kernel/sched/core.c:7848 > Call Trace: > __mutex_lock_common+0xc4/0x2ef0 kernel/locking/mutex.c:935 > __mutex_lock kernel/locking/mutex.c:1103 [inline] > mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1118 > io_wq_submit_work+0x39a/0x720 fs/io_uring.c:6411 > io_run_cancel fs/io-wq.c:856 [inline] > io_wqe_cancel_pending_work fs/io-wq.c:990 [inline] > io_wq_cancel_cb+0x614/0xcb0 fs/io-wq.c:1027 > io_uring_cancel_files fs/io_uring.c:8874 [inline] > io_uring_cancel_task_requests fs/io_uring.c:8952 [inline] > __io_uring_files_cancel+0x115d/0x19e0 fs/io_uring.c:9038 > io_uring_files_cancel include/linux/io_uring.h:51 [inline] > do_exit+0x2e6/0x2490 kernel/exit.c:780 > do_group_exit+0x168/0x2d0 kernel/exit.c:922 > get_signal+0x16b5/0x2030 kernel/signal.c:2770 > arch_do_signal_or_restart+0x8e/0x6a0 arch/x86/kernel/signal.c:811 > handle_signal_work kernel/entry/common.c:147 [inline] > exit_to_user_mode_loop kernel/entry/common.c:171 [inline] > exit_to_user_mode_prepare+0xac/0x1e0 kernel/entry/common.c:201 > __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] > syscall_exit_to_user_mode+0x48/0x190 kernel/entry/common.c:302 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Rewrite io_uring_cancel_files() to mimic __io_uring_task_cancel()'s > counting scheme, so it does all the heavy work before setting > TASK_UNINTERRUPTIBLE. > > Cc: stable@vger.kernel.org # 5.9+ > Reported-by: syzbot+f655445043a26a7cfab8@syzkaller.appspotmail.com > Signed-off-by: Pavel Begunkov > --- > fs/io_uring.c | 41 ++++++++++++++++++++++++----------------- > 1 file changed, 24 insertions(+), 17 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 09aada153a71..f3f2b37e7021 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -8873,30 +8873,33 @@ static void io_cancel_defer_files(struct io_ring_ctx *ctx, > } > } > > +static int io_uring_count_inflight(struct io_ring_ctx *ctx, > + struct task_struct *task, > + struct files_struct *files) > +{ > + struct io_kiocb *req; > + int cnt = 0; > + > + spin_lock_irq(&ctx->inflight_lock); > + list_for_each_entry(req, &ctx->inflight_list, inflight_entry) { > + if (!io_match_task(req, task, files)) This condition should be inversed. Jens, please drop it p.s. I wonder how tests didn't catch that > + cnt++; > + } > + spin_unlock_irq(&ctx->inflight_lock); > + return cnt; > +} > + > static void io_uring_cancel_files(struct io_ring_ctx *ctx, > struct task_struct *task, > struct files_struct *files) > { > while (!list_empty_careful(&ctx->inflight_list)) { > struct io_task_cancel cancel = { .task = task, .files = files }; > - struct io_kiocb *req; > DEFINE_WAIT(wait); > - bool found = false; > + int inflight; > > - spin_lock_irq(&ctx->inflight_lock); > - list_for_each_entry(req, &ctx->inflight_list, inflight_entry) { > - if (!io_match_task(req, task, files)) > - continue; > - found = true; > - break; > - } > - if (found) > - prepare_to_wait(&task->io_uring->wait, &wait, > - TASK_UNINTERRUPTIBLE); > - spin_unlock_irq(&ctx->inflight_lock); > - > - /* We need to keep going until we don't find a matching req */ > - if (!found) > + inflight = io_uring_count_inflight(ctx, task, files); > + if (!inflight) > break; > > io_wq_cancel_cb(ctx->io_wq, io_cancel_task_cb, &cancel, true); > @@ -8905,7 +8908,11 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx, > io_cqring_overflow_flush(ctx, true, task, files); > /* cancellations _may_ trigger task work */ > io_run_task_work(); > - schedule(); > + > + prepare_to_wait(&task->io_uring->wait, &wait, > + TASK_UNINTERRUPTIBLE); > + if (inflight == io_uring_count_inflight(ctx, task, files)) > + schedule(); > finish_wait(&task->io_uring->wait, &wait); > } > } > -- Pavel Begunkov