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Thu, 04 Feb 2021 05:58:17 -0800 (PST) From: Pavel Begunkov To: Xiaoguang Wang , io-uring@vger.kernel.org Cc: axboe@kernel.dk, joseph.qi@linux.alibaba.com References: <20210204092056.12797-1-xiaoguang.wang@linux.alibaba.com> <150e4e33-5c12-3ae3-9db3-2d85edb94c5f@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== Subject: Re: [PATCH] io_uring: don't modify identity's files uncess identity is cowed Message-ID: <07c0ffc8-ee68-6298-47a3-b1686e3cd0ba@gmail.com> Date: Thu, 4 Feb 2021 13:54:34 +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: <150e4e33-5c12-3ae3-9db3-2d85edb94c5f@gmail.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 04/02/2021 11:05, Pavel Begunkov wrote: > On 04/02/2021 09:20, Xiaoguang Wang wrote: >> Abaci Robot reported following panic: >> BUG: kernel NULL pointer dereference, address: 0000000000000000 >> PGD 800000010ef3f067 P4D 800000010ef3f067 PUD 10d9df067 PMD 0 >> Oops: 0002 [#1] SMP PTI >> CPU: 0 PID: 1869 Comm: io_wqe_worker-0 Not tainted 5.11.0-rc3+ #1 >> Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 >> RIP: 0010:put_files_struct+0x1b/0x120 >> Code: 24 18 c7 00 f4 ff ff ff e9 4d fd ff ff 66 90 0f 1f 44 00 00 41 57 41 56 49 89 fe 41 55 41 54 55 53 48 83 ec 08 e8 b5 6b db ff 41 ff 0e 74 13 48 83 c4 08 5b 5d 41 5c 41 5d 41 5e 41 5f e9 9c >> RSP: 0000:ffffc90002147d48 EFLAGS: 00010293 >> RAX: 0000000000000000 RBX: ffff88810d9a5300 RCX: 0000000000000000 >> RDX: ffff88810d87c280 RSI: ffffffff8144ba6b RDI: 0000000000000000 >> RBP: 0000000000000080 R08: 0000000000000001 R09: ffffffff81431500 >> R10: ffff8881001be000 R11: 0000000000000000 R12: ffff88810ac2f800 >> R13: ffff88810af38a00 R14: 0000000000000000 R15: ffff8881057130c0 >> FS: 0000000000000000(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 0000000000000000 CR3: 000000010dbaa002 CR4: 00000000003706f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> __io_clean_op+0x10c/0x2a0 >> io_dismantle_req+0x3c7/0x600 >> __io_free_req+0x34/0x280 >> io_put_req+0x63/0xb0 >> io_worker_handle_work+0x60e/0x830 >> ? io_wqe_worker+0x135/0x520 >> io_wqe_worker+0x158/0x520 >> ? __kthread_parkme+0x96/0xc0 >> ? io_worker_handle_work+0x830/0x830 >> kthread+0x134/0x180 >> ? kthread_create_worker_on_cpu+0x90/0x90 >> ret_from_fork+0x1f/0x30 >> Modules linked in: >> CR2: 0000000000000000 >> ---[ end trace c358ca86af95b1e7 ]--- >> >> I guess case below can trigger above panic: there're two threads which >> operates different io_uring ctxs and share same sqthread identity, and >> later one thread exits, io_uring_cancel_task_requests() will clear >> task->io_uring->identity->files to be NULL in sqpoll mode, then another >> ctx that uses same identity will panic. >> >> Indeed we don't need to clear task->io_uring->identity->files here, >> io_grab_identity() should handle identity->files changes well, if >> task->io_uring->identity->files is not equal to current->files, >> io_cow_identity() should handle this changes well. > > Didn't look in the trace above, but the change looks good. I even did > it myself a couple of weeks ago, but it got dropped because of unrelated > hassle. > > I'll test/review a bit later. Reviewed-by: Pavel Begunkov Cc: stable@vger.kernel.org # 5.5+ > >> >> Reported-by: Abaci Robot >> Signed-off-by: Xiaoguang Wang >> --- >> fs/io_uring.c | 6 ------ >> 1 file changed, 6 deletions(-) >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index 38c6cbe1ab38..5d3348d66f06 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -8982,12 +8982,6 @@ static void io_uring_cancel_task_requests(struct io_ring_ctx *ctx, >> >> if ((ctx->flags & IORING_SETUP_SQPOLL) && ctx->sq_data) { >> atomic_dec(&task->io_uring->in_idle); >> - /* >> - * If the files that are going away are the ones in the thread >> - * identity, clear them out. >> - */ >> - if (task->io_uring->identity->files == files) >> - task->io_uring->identity->files = NULL; >> io_sq_thread_unpark(ctx->sq_data); >> } >> } >> > -- Pavel Begunkov