netdev - Re: [PATCH bpf-next] selftests/bpf: fix sample

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 2 Jun 2020 09:18:16 -0700
From:   Song Liu <song@...nel.org>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next] selftests/bpf: fix sample_cnt shared between two threads

On Mon, Jun 1, 2020 at 10:04 PM Andrii Nakryiko <andriin@...com> wrote:
>
> Make sample_cnt volatile to fix possible selftests failure due to compiler
> optimization preventing latest sample_cnt value to be visible to main thread.
> sample_cnt is incremented in background thread, which is then joined into main
> thread. So in terms of visibility sample_cnt update is ok. But because it's
> not volatile, compiler might make optimizations that would prevent main thread
> to see latest updated value. Fix this by marking global variable volatile.
>
> Fixes: cb1c9ddd5525 ("selftests/bpf: Add BPF ringbuf selftests")
> Signed-off-by: Andrii Nakryiko <andriin@...com>

Acked-by: Song Liu <songliubraving@...com>