linux-kernel - Re: PROBLEM: syzkaller found / reduced C repro for non-fatal unchecked MSR access error

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Date:   Fri, 11 Jan 2019 11:02:53 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Esme <esploit@...tonmail.ch>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        JJiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: PROBLEM: syzkaller found / reduced C repro for non-fatal
 unchecked MSR access error

On Thu, Jan 10, 2019 at 11:21:16PM +0000, Esme wrote:
> Attached is a fairly small C repro I did not see any references to
> this possible flaw (unchecked MSR access) in relation to
> __NR_perf_event_open
> 
> Attached is the config directly extracted from proc.  This is the call
> stack in relation to the MSR access error (5.0.0-rc1+), I get a very
> similar stack running this test case on a stock Ubuntu
> "4.18.0-11-generic" (pasted after this one).

> -- Esme
> 
> [   70.228744] unchecked MSR access error: WRMSR to 0xc0010000 (tried to write 0x0000020000130076) at rIP: 0xffffffff812dde28 (native_write_msr+0x8/0x30)

That's K7_EVNTSEL0. What kind of hardware are you running this on?