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Date: Thu, 27 Aug 2020 07:49:45 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Stefano Garzarella <sgarzare@...hat.com>
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 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.
> 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.
--
Jens Axboe
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