From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Dmitrii Banshchikov <me@ubique.spb.ru>
Cc: bpf <bpf@vger.kernel.org>, 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>,
Network Development <netdev@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrey Ignatov <rdna@fb.com>
Subject: Re: [PATCH bpf v2 0/2] Forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing progs
Date: Sun, 14 Nov 2021 10:38:31 -0800 [thread overview]
Message-ID: <CAADnVQ+zo-DMC=yqqphEno9pxwhBQ3soQzKd=2yLPNoLyBcFHw@mail.gmail.com> (raw)
In-Reply-To: <20211113142227.566439-1-me@ubique.spb.ru>
On Sat, Nov 13, 2021 at 6:22 AM Dmitrii Banshchikov <me@ubique.spb.ru> wrote:
>
> Various locking issues are possible with bpf_ktime_get_coarse_ns() and
> bpf_timer_* set of helpers.
>
> syzbot found a locking issue with bpf_ktime_get_coarse_ns() helper executed in
> BPF_PROG_TYPE_PERF_EVENT prog type - [1]. The issue is possible because the
> helper uses non fast version of time accessor that isn't safe for any context.
> The helper was added because it provided performance benefits in comparison to
> bpf_ktime_get_ns() helper.
>
> A similar locking issue is possible with bpf_timer_* set of helpers when used
> in tracing progs.
>
> The solution is to restrict use of the helpers in tracing progs.
>
> In the [1] discussion it was stated that bpf_spin_lock related helpers shall
> also be excluded for tracing progs. The verifier has a compatibility check
> between a map and a program. If a tracing program tries to use a map which
> value has struct bpf_spin_lock the verifier fails that is why bpf_spin_lock is
> already restricted.
>
> Patch 1 restricts helpers
> Patch 2 adds tests
>
> v1 -> v2:
> * Limit the helpers via func proto getters instead of allowed callback
> * Add note about helpers' restrictions to linux/bpf.h
> * Add Fixes tag
> * Remove extra \0 from btf_str_sec
> * Beside asm tests add prog tests
> * Trim CC
>
> 1. https://lore.kernel.org/all/00000000000013aebd05cff8e064@google.com/
Applied. Thanks
next prev parent reply other threads:[~2021-11-14 18:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-13 14:22 [PATCH bpf v2 0/2] Forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing progs Dmitrii Banshchikov
2021-11-13 14:22 ` [PATCH bpf v2 1/2] bpf: " Dmitrii Banshchikov
2021-11-16 2:02 ` Thomas Gleixner
2021-11-16 4:44 ` Alexei Starovoitov
2021-11-13 14:22 ` [PATCH bpf v2 2/2] selftests/bpf: Add tests for restricted helpers Dmitrii Banshchikov
2021-11-14 18:38 ` Alexei Starovoitov [this message]
2021-11-16 2:18 ` [PATCH bpf v2 0/2] Forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing progs Thomas Gleixner
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