From: Pavel Begunkov <asml.silence@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: io-uring@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Horst Schirmeier <horst.schirmeier@tu-dortmund.de>,
"Franz-B . Tuneke" <franz-bernhard.tuneke@tu-dortmund.de>,
Christian Dietrich <stettberger@dokucode.de>
Subject: Re: [PATCH 15/23] io_uring: enable BPF to submit SQEs
Date: Fri, 21 May 2021 10:33:50 +0100 [thread overview]
Message-ID: <a5cc80c8-5dea-031f-703e-cc18d6625ad6@gmail.com> (raw)
In-Reply-To: <20210521010752.lky4pz7zipefrfr7@ast-mbp>
On 5/21/21 2:07 AM, Alexei Starovoitov wrote:
> 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?
Actual submission may be moved out of BPF, so enabling it for both, but
the question I wonder about is what are the plans for sleepable
programs? E.g. if it's a marginal features much limited in
functionality, e.g. iirc as it's not allowed to use some BPF data
types, it may not worth doing.
>
>> + if (unlikely(!req))
>> + return -ENOMEM;
>> + if (!percpu_ref_tryget_many(&ctx->refs, 1)) {
>> + kmem_cache_free(req_cachep, req);
>> + return -EAGAIN;
>> + }
>> + percpu_counter_add(¤t->io_uring->inflight, 1);
>> + refcount_add(1, ¤t->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?
It works on memory rw shared with userspace, so it already assumes
the worst
> 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.
Thanks for taking a look! I have no idea what bpf_link is, need
to check it out
--
Pavel Begunkov
next prev parent reply other threads:[~2021-05-21 9:34 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
2021-05-21 9:33 ` Pavel Begunkov [this message]
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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