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Wed, 05 Feb 2020 09:00:01 -0800 (PST) Received: from [192.168.43.239] ([109.126.145.62]) by smtp.gmail.com with ESMTPSA id a7sm39870ejr.30.2020.02.05.09.00.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Feb 2020 09:00:01 -0800 (PST) Subject: Re: [PATCH] io_uring: fix mm use with IORING_OP_{READ,WRITE} To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <951bb84c8337aaac7654261a21b03506b2b8a001.1580914723.git.asml.silence@gmail.com> <62e33e81-7857-fb5c-92be-6757623a6478@gmail.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== Message-ID: <0c947713-64e2-1670-7ca4-18838fbaf096@gmail.com> Date: Wed, 5 Feb 2020 19:59:13 +0300 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: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="TOK6zagsvseVUmcfSevEPkkpIpuNQIJBU" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --TOK6zagsvseVUmcfSevEPkkpIpuNQIJBU Content-Type: multipart/mixed; boundary="USU9GwRdfKxAKn8OjhOUZABzgrPT8IHbc"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <0c947713-64e2-1670-7ca4-18838fbaf096@gmail.com> Subject: Re: [PATCH] io_uring: fix mm use with IORING_OP_{READ,WRITE} References: <951bb84c8337aaac7654261a21b03506b2b8a001.1580914723.git.asml.silence@gmail.com> <62e33e81-7857-fb5c-92be-6757623a6478@gmail.com> In-Reply-To: --USU9GwRdfKxAKn8OjhOUZABzgrPT8IHbc Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 05/02/2020 19:52, Jens Axboe wrote: > On 2/5/20 9:50 AM, Pavel Begunkov wrote: >> On 05/02/2020 19:16, Jens Axboe wrote: >>> On 2/5/20 9:05 AM, Jens Axboe wrote: >>>> On 2/5/20 9:02 AM, Pavel Begunkov wrote: >>>>> On 05/02/2020 18:54, Jens Axboe wrote: >>>>>> On 2/5/20 8:46 AM, Pavel Begunkov wrote: >>>>>>> IORING_OP_{READ,WRITE} need mm to access user buffers, hence >>>>>>> req->has_user check should go for them as well. Move the correspo= nding >>>>>>> imports past the check. >>>>>> >>>>>> I'd need to double check, but I think the has_user check should ju= st go. >>>>>> The import checks for access anyway, so we'll -EFAULT there if we >>>>>> somehow messed up and didn't acquire the right mm. >>>>>> >>>>> It'd be even better. I have plans to remove it, but I was thinking = from a >>>>> different angle. >>>> >>>> Let me just confirm it in practice, but it should be fine. Then we c= an just >>>> kill it. >>> >>> OK now I remember - in terms of mm it's fine, we'll do the right thin= g. >>> But the iov_iter_init() has this gem: >>> >>> /* It will get better. Eventually... */ >>> if (uaccess_kernel()) { >>> i->type =3D ITER_KVEC | direction; >>> i->kvec =3D (struct kvec *)iov; >>> } else { >>> i->type =3D ITER_IOVEC | direction; >>> i->iov =3D iov; >>> } >>> >>> which means that if we haven't set USER_DS, then iov_iter_init() will= >>> magically set the type to ITER_KVEC which then crashes when the itera= tor >>> tries to copy. >>> >>> Which is pretty lame. How about a patch that just checks for >>> uaccess_kernel() and -EFAULTs if true for the non-fixed variants wher= e >>> we don't init the iter ourselves? Then we can still kill req->has_use= r >>> and not have to fill it in. >>> >>> >> On the other hand, we don't send requests async without @mm. So, if we= fail them >> whenever can't grab mm, it solves all the problems even without extra = checks. >> What do you think? >=20 > I agree, the check is/was just there as a safe guard, it's not really > needed. >=20 Cool, I'll deal with it. --=20 Pavel Begunkov --USU9GwRdfKxAKn8OjhOUZABzgrPT8IHbc-- --TOK6zagsvseVUmcfSevEPkkpIpuNQIJBU Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl469GsACgkQWt5b1Glr +6W2yQ/9FIhV/9U8VB3Mc5pvNuexGv4wRrWFw8RNBdFMCljEfITID4PhgWWY4Qig lOl7C/vqvCuIAi1qL6cajWNY0kWjqj8O9wm6mqCRmgRPhu7EUyTjRBeLWMz+nQe6 CtNvaKUkoMkRYJdhdtZKJLhAfPjGH/nNDkp5ncRNBGngzaFOfHjQhBvk6GhYDolS HdY1WRpxoxaa23EMBBoj5nsJIHbjLz83QmnXRQWBOKhk/VO5RcP+aaun3YGhH8nR 3kkL7Io2QXKTrgUeooZmAehXVJmhE0DfKwsk+gxQ0SHYR/KyJmeuqb/Uf34dtsUe OnxUSmxOjQkvNkvzDL52Rm8ma0q+huJAGckDq/zkfJmqLTzRruCWuN0PhD169FWh zedUIs23Ybv6nNmMsIWnVIvz1ujqo7DfRUSJZj27Nv8T/7MR2gSWiusM3fDm4WuG P5+YhkruLd4eOZRrleHwrLZ0y5yXRzi9D9N0yTBMeNgVYSuy3HFfw3cULY1d9W0I geUeGHKjZ/hDNcGHMdDrdeKHBdP2vBbBFLpUkOQmPAAsKD1mMd3ZEv7m5VDDsAXC uNSbkkPue2AdWqEylcNalRI1GFGdiLPwNiab9TwGV+8L4iTARCREnK1xROvXFu3q SrxDHhmDysQFmAkPCudkZmAg57PZYr5oJ6XkRLdZndChjHGlrdk= =9HZb -----END PGP SIGNATURE----- --TOK6zagsvseVUmcfSevEPkkpIpuNQIJBU--