netdev - Re: [PATCH net-next 2/3] bpf: introduce BPF_MAP_TYPE_STACK

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: <20160225165005.GU6356@twins.programming.kicks-ass.net>
Date:	Thu, 25 Feb 2016 17:50:05 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexei Starovoitov <ast@...com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Wang Nan <wangnan0@...wei.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] bpf: introduce BPF_MAP_TYPE_STACK_TRACE

On Thu, Feb 25, 2016 at 08:42:40AM -0800, Alexei Starovoitov wrote:
> On 2/25/16 6:23 AM, Peter Zijlstra wrote:
> >>+	id = hash & (smap->n_buckets - 1);
> >Its not at all clear where the corresponding rcu_read_lock() is at.
> >
> >>>+	bucket = rcu_dereference(smap->buckets[id]);
> 
> bpf programs of all types are always executing under rcu_read_lock().
> This is fundamental for maps and majority of the helpers
> that's why there is no WARN_ON(rcu_read_lock_held) in this helper,
> since we already have it in many other places.
> The rcu_read_lock() for kprobe type is in trace_call_bpf().

OK, just not clear from reading this patch in isolation I suppose.