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[109.152.100.164]) by smtp.gmail.com with ESMTPSA id o3sm7600346wru.15.2020.11.07.13.57.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Nov 2020 13:57:15 -0800 (PST) From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, Josef Grieb References: <24446f4e23e80803d3ab1a4d27a6d1a605e37b32.1604783766.git.asml.silence@gmail.com> <39db5769-5aef-96f5-305c-2a3250d9ba73@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 5.11] io_uring: NULL files dereference by SQPOLL Message-ID: <030c3ccb-8777-9c28-1835-5afbbb1c3eb1@gmail.com> Date: Sat, 7 Nov 2020 21:54:13 +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: <39db5769-5aef-96f5-305c-2a3250d9ba73@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 07/11/2020 21:18, Pavel Begunkov wrote: > On 07/11/2020 21:16, Pavel Begunkov wrote: >> SQPOLL task may find sqo_task->files == NULL, so >> __io_sq_thread_acquire_files() would left it unset and so all the >> following fails, e.g. attempts to submit. Fail if sqo_task doesn't have >> files. > > Josef, could you try this one? Hmm, as you said it happens often... IIUC there is a drawback with SQPOLL -- after the creator process/thread exits most of subsequent requests will start failing. I'd say from application correctness POV such tasks should exit only after their SQPOLL io_urings got killed. > >> >> [ 118.962785] BUG: kernel NULL pointer dereference, address: >> 0000000000000020 >> [ 118.963812] #PF: supervisor read access in kernel mode >> [ 118.964534] #PF: error_code(0x0000) - not-present page >> [ 118.969029] RIP: 0010:__fget_files+0xb/0x80 >> [ 119.005409] Call Trace: >> [ 119.005651] fget_many+0x2b/0x30 >> [ 119.005964] io_file_get+0xcf/0x180 >> [ 119.006315] io_submit_sqes+0x3a4/0x950 >> [ 119.006678] ? io_double_put_req+0x43/0x70 >> [ 119.007054] ? io_async_task_func+0xc2/0x180 >> [ 119.007481] io_sq_thread+0x1de/0x6a0 >> [ 119.007828] kthread+0x114/0x150 >> [ 119.008135] ? __ia32_sys_io_uring_enter+0x3c0/0x3c0 >> [ 119.008623] ? kthread_park+0x90/0x90 >> [ 119.008963] ret_from_fork+0x22/0x30 >> >> Reported-by: Josef Grieb >> Signed-off-by: Pavel Begunkov >> --- >> fs/io_uring.c | 19 ++++++++++++------- >> 1 file changed, 12 insertions(+), 7 deletions(-) >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index 8d721a652d61..9c035c5c4080 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -1080,7 +1080,7 @@ static void io_sq_thread_drop_mm_files(void) >> } >> } >> >> -static void __io_sq_thread_acquire_files(struct io_ring_ctx *ctx) >> +static int __io_sq_thread_acquire_files(struct io_ring_ctx *ctx) >> { >> if (!current->files) { >> struct files_struct *files; >> @@ -1091,7 +1091,7 @@ static void __io_sq_thread_acquire_files(struct io_ring_ctx *ctx) >> files = ctx->sqo_task->files; >> if (!files) { >> task_unlock(ctx->sqo_task); >> - return; >> + return -EFAULT; >> } >> atomic_inc(&files->count); >> get_nsproxy(ctx->sqo_task->nsproxy); >> @@ -1105,6 +1105,7 @@ static void __io_sq_thread_acquire_files(struct io_ring_ctx *ctx) >> current->thread_pid = thread_pid; >> task_unlock(current); >> } >> + return 0; >> } >> >> static int __io_sq_thread_acquire_mm(struct io_ring_ctx *ctx) >> @@ -1136,15 +1137,19 @@ static int io_sq_thread_acquire_mm_files(struct io_ring_ctx *ctx, >> struct io_kiocb *req) >> { >> const struct io_op_def *def = &io_op_defs[req->opcode]; >> + int ret; >> >> if (def->work_flags & IO_WQ_WORK_MM) { >> - int ret = __io_sq_thread_acquire_mm(ctx); >> + ret = __io_sq_thread_acquire_mm(ctx); >> if (unlikely(ret)) >> return ret; >> } >> >> - if (def->needs_file || (def->work_flags & IO_WQ_WORK_FILES)) >> - __io_sq_thread_acquire_files(ctx); >> + if (def->needs_file || (def->work_flags & IO_WQ_WORK_FILES)) { >> + ret = __io_sq_thread_acquire_files(ctx); >> + if (unlikely(ret)) >> + return ret; >> + } >> >> return 0; >> } >> @@ -2117,8 +2122,8 @@ static void __io_req_task_submit(struct io_kiocb *req) >> { >> struct io_ring_ctx *ctx = req->ctx; >> >> - if (!__io_sq_thread_acquire_mm(ctx)) { >> - __io_sq_thread_acquire_files(ctx); >> + if (!__io_sq_thread_acquire_mm(ctx) && >> + !__io_sq_thread_acquire_files(ctx)) { >> mutex_lock(&ctx->uring_lock); >> __io_queue_sqe(req, NULL); >> mutex_unlock(&ctx->uring_lock); >> > -- Pavel Begunkov