kernel-hardening - Re: [PATCH RFC v2 2/3] io_uring: add IOURING_REGISTER

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Date: Fri, 17 Jul 2020 10:55:17 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Kees Cook <keescook@...omium.org>, Aleksa Sarai <asarai@...e.de>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Christian Brauner <christian.brauner@...ntu.com>,
	Sargun Dhillon <sargun@...gun.me>, Jann Horn <jannh@...gle.com>,
	io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Jeff Moyer <jmoyer@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 2/3] io_uring: add IOURING_REGISTER_RESTRICTIONS
 opcode

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.
> 

I'm not sure I got your point.

Do you mean two different register ops?
For example, maybe with better names... ;-):

	IORING_REGISTER_RESTRICTIONS_OPS
	IORING_REGISTER_RESTRICTIONS_OTHERS


Or a single register op like now, and a new restriction opcode adding
also a new field in the struct io_uring_restriction?
For example:

	struct io_uring_restriction {
		__u16 opcode;
		union {
			__u8 register_op; /* IORING_RESTRICTION_REGISTER_OP */
			__u8 sqe_op;      /* IORING_RESTRICTION_SQE_OP */
			__u8 restriction; /* IORING_RESTRICTION_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,

		IORING_RESTRICTION_OP,

		IORING_RESTRICTION_LAST
	};

	enum {
		/* Only allow fixed files */
		IORING_RESTRICTION_OP_FIXED_FILES_ONLY,
	};


Thanks,
Stefano

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