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[109.152.100.135]) by smtp.gmail.com with ESMTPSA id 35sm13807181wro.71.2020.11.22.08.00.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Nov 2020 08:00:21 -0800 (PST) To: Hillf Danton Cc: syzbot , axboe@kernel.dk, io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk, will@kernel.org References: <0000000000002bea4605b4a5931d@google.com> <20201122030421.2088-1-hdanton@sina.com> <20201122092003.7724-1-hdanton@sina.com> From: Pavel Begunkov 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== Subject: Re: INFO: task hung in __io_uring_files_cancel Message-ID: <03db9ac8-f077-ab84-04e6-b83ad6763fe7@gmail.com> Date: Sun, 22 Nov 2020 15:57:12 +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: <20201122092003.7724-1-hdanton@sina.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 22/11/2020 09:20, Hillf Danton wrote: > On Sun, 22 Nov 2020 03:32:01 +0000 Pavel Begunkov wrote: >> On 22/11/2020 03:04, Hillf Danton wrote: >>> On Sat, 21 Nov 2020 14:35:15 -0800 >>>> syzbot found the following issue on: >>>> >>>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10401726500000 >>>> final oops: https://syzkaller.appspot.com/x/report.txt?x=12401726500000 >>>> console output: https://syzkaller.appspot.com/x/log.txt?x=14401726500000 >>>> >>>> IMPORTANT: if you fix the issue, please add the following tag to the commit: >>>> Reported-by: syzbot+c0d52d0b3c0c3ffb9525@syzkaller.appspotmail.com >>>> Fixes: 4d004099a668 ("lockdep: Fix lockdep recursion") >>>> >>>> INFO: task syz-executor.0:9557 blocked for more than 143 seconds. >>>> Not tainted 5.10.0-rc4-next-20201117-syzkaller #0 >>>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>>> task:syz-executor.0 state:D stack:28584 pid: 9557 ppid: 8485 flags:0x00004002 >>>> Call Trace: >>>> context_switch kernel/sched/core.c:4269 [inline] >>>> __schedule+0x890/0x2030 kernel/sched/core.c:5019 >>>> schedule+0xcf/0x270 kernel/sched/core.c:5098 >>>> io_uring_cancel_files fs/io_uring.c:8720 [inline] >>>> io_uring_cancel_task_requests fs/io_uring.c:8772 [inline] >>>> __io_uring_files_cancel+0xc4d/0x14b0 fs/io_uring.c:8868 >>>> io_uring_files_cancel include/linux/io_uring.h:51 [inline] >>>> exit_files+0xe4/0x170 fs/file.c:456 >>>> do_exit+0xb61/0x29f0 kernel/exit.c:818 >>>> do_group_exit+0x125/0x310 kernel/exit.c:920 >>>> get_signal+0x3ea/0x1f70 kernel/signal.c:2750 >>>> arch_do_signal_or_restart+0x2a6/0x1ea0 arch/x86/kernel/signal.c:811 >>>> handle_signal_work kernel/entry/common.c:145 [inline] >>>> exit_to_user_mode_loop kernel/entry/common.c:169 [inline] >>>> exit_to_user_mode_prepare+0x124/0x200 kernel/entry/common.c:199 >>>> syscall_exit_to_user_mode+0x38/0x260 kernel/entry/common.c:274 >>>> entry_SYSCALL_64_after_hwframe+0x44/0xa9 >>>> RIP: 0033:0x45deb9 >>>> Code: Unable to access opcode bytes at RIP 0x45de8f. >>>> RSP: 002b:00007fa68397ccf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca >>>> RAX: fffffffffffffe00 RBX: 000000000118bf28 RCX: 000000000045deb9 >>>> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000118bf28 >>>> RBP: 000000000118bf20 R08: 0000000000000000 R09: 0000000000000000 >>>> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c >>>> R13: 00007fff50acc9af R14: 00007fa68397d9c0 R15: 000000000118bf2c >>>> >> ... >>> >>> Fix 311daef8013a ("io_uring: replace inflight_wait with tctx->wait") >>> by cutting the pre-condition to wakeup because waitqueue_active() >>> speaks the language in the East End while atomic_read() may speak >>> the language in Paris. >> >> Your description doesn't help, > > That is what I could find to describe the changs added in > 311daef8013a, given that waitqueue_active() and atomic_read() IMO are > primary bricks without natural links prebuilt. I dont think either > of them could be replaced with another even in 311daef8013a. There are not linked, but that doesn't make it automatically wrong. I still don't understand how it fixes the problem, and it's better to find the root cause because there are similar places that might still be similarly flawed. >> why do you think this is the problem? > > This is not a tough question, thanks to the reproducer. > >> ->in_idle is always set when io_uring_cancel_files() sleeps on it, >> and ->inflight_lock should guarantee ordering. > > The syzbot report makes sense, right? > >>> >>> --- a/fs/io_uring.c >>> +++ b/fs/io_uring.c >>> @@ -6082,8 +6082,7 @@ static void io_req_drop_files(struct io_ >>> >>> spin_lock_irqsave(&ctx->inflight_lock, flags); >>> list_del(&req->inflight_entry); >>> - if (atomic_read(&tctx->in_idle)) >>> - wake_up(&tctx->wait); >>> + wake_up(&tctx->wait); >>> spin_unlock_irqrestore(&ctx->inflight_lock, flags); >>> req->flags &= ~REQ_F_INFLIGHT; >>> put_files_struct(req->work.identity->files); -- Pavel Begunkov