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Tue, 21 Jul 2020 10:11:18 -0700 (PDT) Subject: Re: [PATCH RFC v2 2/3] io_uring: add IOURING_REGISTER_RESTRICTIONS opcode To: Stefano Garzarella Cc: Alexander Viro , Kernel Hardening , Kees Cook , Aleksa Sarai , Stefan Hajnoczi , Christian Brauner , Sargun Dhillon , Jann Horn , io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jeff Moyer , linux-kernel@vger.kernel.org References: <20200716124833.93667-1-sgarzare@redhat.com> <20200716124833.93667-3-sgarzare@redhat.com> <0fbb0393-c14f-3576-26b1-8bb22d2e0615@kernel.dk> <20200721104009.lg626hmls5y6ihdr@steredhat> From: Jens Axboe Message-ID: <15f7fcf5-c5bb-7752-fa9a-376c4c7fc147@kernel.dk> Date: Tue, 21 Jul 2020 11:11:17 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200721104009.lg626hmls5y6ihdr@steredhat> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 7/21/20 4:40 AM, Stefano Garzarella wrote: > On Thu, Jul 16, 2020 at 03:26:51PM -0600, Jens Axboe wrote: >> On 7/16/20 6:48 AM, Stefano Garzarella wrote: >>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h >>> index efc50bd0af34..0774d5382c65 100644 >>> --- a/include/uapi/linux/io_uring.h >>> +++ b/include/uapi/linux/io_uring.h >>> @@ -265,6 +265,7 @@ enum { >>> IORING_REGISTER_PROBE, >>> IORING_REGISTER_PERSONALITY, >>> IORING_UNREGISTER_PERSONALITY, >>> + IORING_REGISTER_RESTRICTIONS, >>> >>> /* this goes last */ >>> IORING_REGISTER_LAST >>> @@ -293,4 +294,30 @@ struct io_uring_probe { >>> struct io_uring_probe_op ops[0]; >>> }; >>> >>> +struct io_uring_restriction { >>> + __u16 opcode; >>> + union { >>> + __u8 register_op; /* IORING_RESTRICTION_REGISTER_OP */ >>> + __u8 sqe_op; /* IORING_RESTRICTION_SQE_OP */ >>> + }; >>> + __u8 resv; >>> + __u32 resv2[3]; >>> +}; >>> + >>> +/* >>> + * io_uring_restriction->opcode values >>> + */ >>> +enum { >>> + /* Allow an io_uring_register(2) opcode */ >>> + IORING_RESTRICTION_REGISTER_OP, >>> + >>> + /* Allow an sqe opcode */ >>> + IORING_RESTRICTION_SQE_OP, >>> + >>> + /* Only allow fixed files */ >>> + IORING_RESTRICTION_FIXED_FILES_ONLY, >>> + >>> + IORING_RESTRICTION_LAST >>> +}; >>> + >> >> Not sure I totally love this API. Maybe it'd be cleaner to have separate >> ops for this, instead of muxing it like this. One for registering op >> code restrictions, and one for disallowing other parts (like fixed >> files, etc). >> >> I think that would look a lot cleaner than the above. >> > > Talking with Stefan, an alternative, maybe more near to your suggestion, > would be to remove the 'struct io_uring_restriction' and add the > following register ops: > > /* Allow an sqe opcode */ > IORING_REGISTER_RESTRICTION_SQE_OP > > /* Allow an io_uring_register(2) opcode */ > IORING_REGISTER_RESTRICTION_REG_OP > > /* Register IORING_RESTRICTION_* */ > IORING_REGISTER_RESTRICTION_OP > > > enum { > /* Only allow fixed files */ > IORING_RESTRICTION_FIXED_FILES_ONLY, > > IORING_RESTRICTION_LAST > } > > > We can also enable restriction only when the rings started, to avoid to > register IORING_REGISTER_ENABLE_RINGS opcode. Once rings are started, > the restrictions cannot be changed or disabled. My concerns are largely: 1) An API that's straight forward to use 2) Something that'll work with future changes The "allow these opcodes" is straightforward, and ditto for the register opcodes. The fixed file I guess is the odd one out. So if we need to disallow things in the future, we'll need to add a new restriction sub-op. Should this perhaps be "these flags must be set", and that could easily be augmented with "these flags must not be set"? -- Jens Axboe