netdev - Re: [PATCH bpf-next 3/3] bpf, libbpf: use proper barriers in perf ring buffer walk

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]

Message-ID: <20181017155135.GN3121@hirez.programming.kicks-ass.net>
Date:   Wed, 17 Oct 2018 17:51:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     alexei.starovoitov@...il.com, paulmck@...ux.vnet.ibm.com,
        will.deacon@....com, acme@...hat.com, yhs@...com,
        john.fastabend@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next 3/3] bpf, libbpf: use proper barriers in perf
 ring buffer walk

On Wed, Oct 17, 2018 at 04:41:56PM +0200, Daniel Borkmann wrote:
> +static __u64 bpf_perf_read_head(struct perf_event_mmap_page *header)
> +{
> +	__u64 data_head = READ_ONCE(header->data_head);
> +
> +	smp_rmb();
> +	return data_head;
> +}
> +
> +static void bpf_perf_write_tail(struct perf_event_mmap_page *header,
> +				__u64 data_tail)
> +{
> +	smp_mb();
> +	header->data_tail = data_tail;
> +}

Same coments, either smp_load_acquire()/smp_store_release() or at the
very least a WRITE_ONCE() there.