linux-kernel - Re: hit a KASan bug related to Perf during stress test

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:   Mon, 24 Oct 2016 14:12:02 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        "Ni, BaoleX" <baolex.ni@...el.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "acme@...nel.org" <acme@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "Liu, Chuansheng" <chuansheng.liu@...el.com>,
        Jiri Olsa <jolsa@...nel.org>
Subject: Re: hit a KASan bug related to Perf during stress test

On Mon, Oct 24, 2016 at 02:04:11PM +0200, Jiri Olsa wrote:
> On Mon, Oct 24, 2016 at 01:29:45PM +0200, Peter Zijlstra wrote:

> > Hurm, then again, I imagine that after unhash_process the PID/TID could
> > be instantly re-used and then we're still confused.
> 
> sounds bad.. I haven't checked the related pid_alive code,
> but shouldn't we already get the EXIT event in this case?

It has, perf_event_exit_task() happens before we unhash.

But a per-cpu event that has PID/TID reporting on will run into this.

We'll observe 'funny' values between the unhash and the next context
switch.