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From: Alexei Starovoitov <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: [email protected], [email protected],
	[email protected], [email protected],
	Jens Axboe <[email protected]>, Alexei Starovoitov <[email protected]>,
	Daniel Borkmann <[email protected]>,
	Andrii Nakryiko <[email protected]>,
	Martin KaFai Lau <[email protected]>, Song Liu <[email protected]>,
	Yonghong Song <[email protected]>,
	John Fastabend <[email protected]>,
	KP Singh <[email protected]>,
	Horst Schirmeier <[email protected]>,
	"Franz-B . Tuneke" <[email protected]>,
	Christian Dietrich <[email protected]>
Subject: Re: [PATCH 15/23] io_uring: enable BPF to submit SQEs
Date: Thu, 20 May 2021 18:07:52 -0700	[thread overview]
Message-ID: <20210521010752.lky4pz7zipefrfr7@ast-mbp> (raw)
In-Reply-To: <8ec8373d406d1fcb41719e641799dcc5c0455db3.1621424513.git.asml.silence@gmail.com>

On Wed, May 19, 2021 at 03:13:26PM +0100, Pavel Begunkov wrote:
>  
> +BPF_CALL_3(io_bpf_queue_sqe, struct io_bpf_ctx *,		bpf_ctx,
> +			     const struct io_uring_sqe *,	sqe,
> +			     u32,				sqe_len)
> +{
> +	struct io_ring_ctx *ctx = bpf_ctx->ctx;
> +	struct io_kiocb *req;
> +
> +	if (sqe_len != sizeof(struct io_uring_sqe))
> +		return -EINVAL;
> +
> +	req = io_alloc_req(ctx);

that is GFP_KERNEL allocation.
It's only allowed from sleepable bpf progs and further down
there is a correct check for it, so all good.
But submitting sqe is a fundemntal io_uring operation,
so what is the use case for non-sleepable?
In other words why bother? Allow sleepable only and simplify the code?

> +	if (unlikely(!req))
> +		return -ENOMEM;
> +	if (!percpu_ref_tryget_many(&ctx->refs, 1)) {
> +		kmem_cache_free(req_cachep, req);
> +		return -EAGAIN;
> +	}
> +	percpu_counter_add(&current->io_uring->inflight, 1);
> +	refcount_add(1, &current->usage);
> +
> +	/* returns number of submitted SQEs or an error */
> +	return !io_submit_sqe(ctx, req, sqe);

A buggy bpf prog will be able to pass junk sizeof(struct io_uring_sqe)
as 'sqe' here.
What kind of validation io_submit_sqe() does to avoid crashing the kernel?

General comments that apply to all patches:
- commit logs are way too terse. Pls expand with details.
- describe new bpf helpers in comments in bpf.h. Just adding them to an enum is not enough.
- selftest/bpf are mandatory for all new bpf features.
- consider bpf_link style of attaching bpf progs. We had enough issues with progs
  that get stuck due to application bugs. Auto-detach saves the day more often than not.

  parent reply	other threads:[~2021-05-21  1:07 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-19 14:13 [RFC v2 00/23] io_uring BPF requests Pavel Begunkov
2021-05-19 14:13 ` [PATCH 01/23] io_uring: shuffle rarely used ctx fields Pavel Begunkov
2021-05-20 21:46   ` Song Liu
2021-05-20 22:46     ` Pavel Begunkov
2021-05-19 14:13 ` [PATCH 02/23] io_uring: localise fixed resources fields Pavel Begunkov
2021-05-19 14:13 ` [PATCH 03/23] io_uring: remove dependency on ring->sq/cq_entries Pavel Begunkov
2021-05-19 14:13 ` [PATCH 04/23] io_uring: deduce cq_mask from cq_entries Pavel Begunkov
2021-05-19 14:13 ` [PATCH 05/23] io_uring: kill cached_cq_overflow Pavel Begunkov
2021-05-19 14:13 ` [PATCH 06/23] io_uring: rename io_get_cqring Pavel Begunkov
2021-05-19 14:13 ` [PATCH 07/23] io_uring: extract struct for CQ Pavel Begunkov
2021-05-19 14:13 ` [PATCH 08/23] io_uring: internally pass CQ indexes Pavel Begunkov
2021-05-19 14:13 ` [PATCH 09/23] io_uring: extract cq size helper Pavel Begunkov
2021-05-19 14:13 ` [PATCH 10/23] io_uring: add support for multiple CQs Pavel Begunkov
2021-05-19 14:13 ` [PATCH 11/23] io_uring: enable mmap'ing additional CQs Pavel Begunkov
2021-05-19 14:13 ` [PATCH 12/23] bpf: add IOURING program type Pavel Begunkov
2021-05-20 23:34   ` Song Liu
2021-05-21  0:56     ` Pavel Begunkov
2021-05-19 14:13 ` [PATCH 13/23] io_uring: implement bpf prog registration Pavel Begunkov
2021-05-20 23:45   ` Song Liu
2021-05-21  0:43     ` Pavel Begunkov
2021-05-19 14:13 ` [PATCH 14/23] io_uring: add support for bpf requests Pavel Begunkov
2021-05-21  0:42   ` Pavel Begunkov
2021-05-19 14:13 ` [PATCH 15/23] io_uring: enable BPF to submit SQEs Pavel Begunkov
2021-05-21  0:06   ` Song Liu
2021-05-21  1:07   ` Alexei Starovoitov [this message]
2021-05-21  9:33     ` Pavel Begunkov
2021-05-19 14:13 ` [PATCH 16/23] io_uring: enable bpf to submit CQEs Pavel Begunkov
2021-05-19 14:13 ` [PATCH 17/23] io_uring: enable bpf to reap CQEs Pavel Begunkov
2021-05-19 14:13 ` [PATCH 18/23] libbpf: support io_uring Pavel Begunkov
2021-05-19 17:38   ` Andrii Nakryiko
2021-05-20  9:58     ` Pavel Begunkov
2021-05-20 17:23       ` Andrii Nakryiko
2021-05-19 14:13 ` [PATCH 19/23] io_uring: pass user_data to bpf executor Pavel Begunkov
2021-05-19 14:13 ` [PATCH 20/23] bpf: Add bpf_copy_to_user() helper Pavel Begunkov
2021-05-19 14:13 ` [PATCH 21/23] io_uring: wire bpf copy to user Pavel Begunkov
2021-05-19 14:13 ` [PATCH 22/23] io_uring: don't wait on CQ exclusively Pavel Begunkov
2021-05-19 14:13 ` [PATCH 23/23] io_uring: enable bpf reqs to wait for CQs Pavel Begunkov
2021-05-21  0:35 ` [RFC v2 00/23] io_uring BPF requests Song Liu
2021-05-21  0:58   ` Pavel Begunkov

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