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Message-ID: <20200827140758.mboc7z2us2yqp356@steredhat.lan>
Date: Thu, 27 Aug 2020 16:07:58 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: Aleksa Sarai <asarai@...e.de>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Jann Horn <jannh@...gle.com>, io-uring@...r.kernel.org,
Christian Brauner <christian.brauner@...ntu.com>,
linux-fsdevel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
Stefan Hajnoczi <stefanha@...hat.com>, linux-kernel@...r.kernel.org,
Sargun Dhillon <sargun@...gun.me>,
Kees Cook <keescook@...omium.org>, Jeff Moyer <jmoyer@...hat.com>
Subject: Re: [PATCH v5 2/3] io_uring: add IOURING_REGISTER_RESTRICTIONS opcode
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
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