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Tue, 28 Jan 2020 16:10:40 -0800 (PST) To: Jens Axboe , Stefan Metzmacher Cc: io-uring , Linux API Mailing List References: <688e187a-75dd-89d9-921c-67de228605ce@samba.org> <1ac31828-e915-6180-cdb4-36685442ea75@kernel.dk> <0d4f43d8-a0c4-920b-5b8f-127c1c5a3fad@kernel.dk> <2d7e7fa2-e725-8beb-90b9-6476d48bdb33@gmail.com> <6c401e23-de7c-1fc1-4122-33d53fcf9700@kernel.dk> <35eebae7-76dd-52ee-58b2-4f9e85caee40@kernel.dk> 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: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()? Message-ID: Date: Wed, 29 Jan 2020 03:10:00 +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: <35eebae7-76dd-52ee-58b2-4f9e85caee40@kernel.dk> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="lRrc6G6gXrup0csTFFZcEntNplhztBpnq" 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) --lRrc6G6gXrup0csTFFZcEntNplhztBpnq Content-Type: multipart/mixed; boundary="cK8FbgRep79RadR9iuAsWyEL8b1jMSHXS"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , Stefan Metzmacher Cc: io-uring , Linux API Mailing List Message-ID: Subject: Re: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()? References: <688e187a-75dd-89d9-921c-67de228605ce@samba.org> <1ac31828-e915-6180-cdb4-36685442ea75@kernel.dk> <0d4f43d8-a0c4-920b-5b8f-127c1c5a3fad@kernel.dk> <2d7e7fa2-e725-8beb-90b9-6476d48bdb33@gmail.com> <6c401e23-de7c-1fc1-4122-33d53fcf9700@kernel.dk> <35eebae7-76dd-52ee-58b2-4f9e85caee40@kernel.dk> In-Reply-To: <35eebae7-76dd-52ee-58b2-4f9e85caee40@kernel.dk> --cK8FbgRep79RadR9iuAsWyEL8b1jMSHXS Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 29/01/2020 02:51, Jens Axboe wrote: > On 1/28/20 4:40 PM, Jens Axboe wrote: >> On 1/28/20 4:36 PM, Pavel Begunkov wrote: >>> On 28/01/2020 22:42, Jens Axboe wrote: >>>> I didn't like it becoming a bit too complicated, both in terms of >>>> implementation and use. And the fact that we'd have to jump through >>>> hoops to make this work for a full chain. >>>> >>>> So I punted and just added sqe->personality and IOSQE_PERSONALITY. >>>> This makes it way easier to use. Same branch: >>>> >>>> https://git.kernel.dk/cgit/linux-block/log/?h=3Dfor-5.6/io_uring-vfs= -creds >>>> >>>> I'd feel much better with this variant for 5.6. >>>> >>> >>> Checked out ("don't use static creds/mm assignments") >>> >>> 1. do we miscount cred refs? We grab one in get_current_cred() for ea= ch async >>> request, but if (worker->creds !=3D work->creds) it will never be put= =2E >> >> Yeah I think you're right, that needs a bit of fixing up. >=20 Hmm, it seems it leaks it unconditionally, as it grabs in a ref in overri= de_creds(). > I think this may have gotten fixed with the later addition posted today= ? > I'll double check. But for the newer stuff, we put it for both cases > when the request is freed. Yeah, maybe. I got tangled trying to verify both at once and decided to s= tart with the old one. >>> 2. shouldn't worker->creds be named {old,saved,etc}_creds? It's set a= s >>> >>> worker->creds =3D override_creds(work->creds); >>> >>> Where override_creds() returns previous creds. And if so, then the fo= llowing >>> fast check looks strange: >>> >>> worker->creds !=3D work->creds >> >> Don't care too much about the naming, but the logic does appear off. >> I'll take a look at both of these tonight, unless you beat me to it. Apparently, you're faster :) >=20 > Testing this now, what a braino. >=20 > diff --git a/fs/io-wq.c b/fs/io-wq.c > index ee49e8852d39..8fbbadf04cc3 100644 > --- a/fs/io-wq.c > +++ b/fs/io-wq.c > @@ -56,7 +56,8 @@ struct io_worker { > =20 > struct rcu_head rcu; > struct mm_struct *mm; > - const struct cred *creds; > + const struct cred *cur_creds; > + const struct cred *saved_creds; > struct files_struct *restore_files; > }; > =20 > @@ -135,9 +136,9 @@ static bool __io_worker_unuse(struct io_wqe *wqe, s= truct io_worker *worker) > { > bool dropped_lock =3D false; > =20 > - if (worker->creds) { > - revert_creds(worker->creds); > - worker->creds =3D NULL; > + if (worker->saved_creds) { > + revert_creds(worker->saved_creds); > + worker->cur_creds =3D worker->saved_creds =3D NULL; > } > =20 > if (current->files !=3D worker->restore_files) { > @@ -424,10 +425,11 @@ static void io_wq_switch_mm(struct io_worker *wor= ker, struct io_wq_work *work) > static void io_wq_switch_creds(struct io_worker *worker, > struct io_wq_work *work) > { > - if (worker->creds) > - revert_creds(worker->creds); > + if (worker->saved_creds) > + revert_creds(worker->saved_creds); > =20 > - worker->creds =3D override_creds(work->creds); > + worker->saved_creds =3D override_creds(work->creds); > + worker->cur_creds =3D work->creds; > } How about as follows? rever_creds() is a bit heavier than put_creds(). static void io_wq_switch_creds(struct io_worker *worker, struct io_wq_work *work) { const struct cred *old_creds =3D override_creds(work->creds); if (worker->saved_creds) put_cred(old_creds); else worker->saved_creds =3D old; worker->cur_creds =3D work->creds; } > =20 > static void io_worker_handle_work(struct io_worker *worker) > @@ -480,7 +482,7 @@ static void io_worker_handle_work(struct io_worker = *worker) > } > if (work->mm !=3D worker->mm) > io_wq_switch_mm(worker, work); > - if (worker->creds !=3D work->creds) > + if (worker->cur_creds !=3D work->creds) > io_wq_switch_creds(worker, work); > /* > * OK to set IO_WQ_WORK_CANCEL even for uncancellable work, >=20 --=20 Pavel Begunkov --cK8FbgRep79RadR9iuAsWyEL8b1jMSHXS-- --lRrc6G6gXrup0csTFFZcEntNplhztBpnq Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl4wzVgACgkQWt5b1Glr +6UP7g//TrctzFamRv2q68uGare3sGHZxaIeAkesfEeJM/ltrvQuh/MIIiWnAdlo 3EE7j5ycRgDpviTaNLd43J3wAGHbz4eZHBeBw9opFkjiAbZird6Etc7+ysLFuojO B8xBhcAfnMN80L4Rb9PTWk6d2pn74YI25mWQxxsbZ2VB44INycF12n1zmeNTF5C7 vOtvr20FVWKE7qDQYbxWbFHhbA0F5btMROOTAqWUtwg0u5sNfgXBst5xKh5yfbjL fj2L3l2aJIhXHzUNFK7pidZw/3/d9RQrpbw6mPcUEdy8wOX7xSaj6KvVRnyLxBx1 wR7Cwm4Kgb5PGEv4lM8NfFR6a6bafB3q0RPsQjyfi6deNoh55PpqdG3P3tUe/7za pHOQ5sm1WIypEgnz2pTPt0D6UxGGji9fI43ihugnB4ju/gLYVf2EG8CUykKUnHFB a83suNfXTKnBR2tub/7Esc2oJ37uX/Um3mYMkXesmempLD+WfSQnaXS+F1mPpD74 hl5LtPhB+tAVExUcZGF78JXogGnUJvbAcdn26nqoq0YPbETMelnGQXWw9+4Ibhik VtZNOqTU9SygfmHjWlchrvtG/6sckWsmxjvl+YFMlRCR6q+NF2GoiRASrRt8dfUA t8kwYMIfclv2iqxyLhbJNqDMklj4/KpZS8nRFBv6SeZbU8zmg9Y= =idCk -----END PGP SIGNATURE----- --lRrc6G6gXrup0csTFFZcEntNplhztBpnq--