Re: [PATCH v5 2/3] io_uring: add IOURING_REGISTER_RESTRICTIONS opcode

[Stefano Garzarella]

On Thu, Aug 27, 2020 at 07:49:45AM -0600, Jens Axboe wrote:
> On 8/27/20 7:40 AM, Stefano Garzarella wrote:
> > @@ -6414,6 +6425,19 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
> >  	if (unlikely(sqe_flags & ~SQE_VALID_FLAGS))
> >  		return -EINVAL;
> >  
> > +	if (unlikely(ctx->restricted)) {
> > +		if (!test_bit(req->opcode, ctx->restrictions.sqe_op))
> > +			return -EACCES;
> > +
> > +		if ((sqe_flags & ctx->restrictions.sqe_flags_required) !=
> > +		    ctx->restrictions.sqe_flags_required)
> > +			return -EACCES;
> > +
> > +		if (sqe_flags & ~(ctx->restrictions.sqe_flags_allowed |
> > +				  ctx->restrictions.sqe_flags_required))
> > +			return -EACCES;
> > +	}
> > +
> 
> This should be a separate function, ala:
> 
> if (unlikely(ctx->restricted)) {
> 	ret = io_check_restriction(ctx, req);
> 	if (ret)
> 		return ret;
> }
> 
> to move it totally out of the (very) hot path.

I'll fix.

> 
> >  	if ((sqe_flags & IOSQE_BUFFER_SELECT) &&
> >  	    !io_op_defs[req->opcode].buffer_select)
> >  		return -EOPNOTSUPP;
> > @@ -8714,6 +8738,71 @@ static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
> >  	return -EINVAL;
> >  }
> >  
> > +static int io_register_restrictions(struct io_ring_ctx *ctx, void __user *arg,
> > +				    unsigned int nr_args)
> > +{
> > +	struct io_uring_restriction *res;
> > +	size_t size;
> > +	int i, ret;
> > +
> > +	/* We allow only a single restrictions registration */
> > +	if (ctx->restricted)
> > +		return -EBUSY;
> > +
> > +	if (!arg || nr_args > IORING_MAX_RESTRICTIONS)
> > +		return -EINVAL;
> > +
> > +	size = array_size(nr_args, sizeof(*res));
> > +	if (size == SIZE_MAX)
> > +		return -EOVERFLOW;
> > +
> > +	res = memdup_user(arg, size);
> > +	if (IS_ERR(res))
> > +		return PTR_ERR(res);
> > +
> > +	for (i = 0; i < nr_args; i++) {
> > +		switch (res[i].opcode) {
> > +		case IORING_RESTRICTION_REGISTER_OP:
> > +			if (res[i].register_op >= IORING_REGISTER_LAST) {
> > +				ret = -EINVAL;
> > +				goto out;
> > +			}
> > +
> > +			__set_bit(res[i].register_op,
> > +				  ctx->restrictions.register_op);
> > +			break;
> > +		case IORING_RESTRICTION_SQE_OP:
> > +			if (res[i].sqe_op >= IORING_OP_LAST) {
> > +				ret = -EINVAL;
> > +				goto out;
> > +			}
> > +
> > +			__set_bit(res[i].sqe_op, ctx->restrictions.sqe_op);
> > +			break;
> > +		case IORING_RESTRICTION_SQE_FLAGS_ALLOWED:
> > +			ctx->restrictions.sqe_flags_allowed = res[i].sqe_flags;
> > +			break;
> > +		case IORING_RESTRICTION_SQE_FLAGS_REQUIRED:
> > +			ctx->restrictions.sqe_flags_required = res[i].sqe_flags;
> > +			break;
> > +		default:
> > +			ret = -EINVAL;
> > +			goto out;
> > +		}
> > +	}
> > +
> > +	ctx->restricted = 1;
> > +
> > +	ret = 0;
> 
> I'd set ret = 0 above the switch, that's the usual idiom - start at
> zero, have someone set it to -ERROR if something fails.

Yes, it is better. I'll fix it.

Thanks,
Stefano