linux-kernel - Re: [PATCH] perf: top: fix a segfault when kernel map is restricted.

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Message-ID: <20150429221203.GD29633@kernel.org>
Date:	Wed, 29 Apr 2015 19:12:03 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	a.p.zijlstra@...llo.nl, paulus@...ba.org0, dsahern@...il.com,
	jolsa@...nel.org, mingo@...hat.com, lizefan@...wei.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: top: fix a segfault when kernel map is restricted.

Em Fri, Apr 24, 2015 at 11:35:29PM +0000, Wang Nan escreveu:
> Perf top raise a warning if a kernel sample is collected but kernel map
> is restricted. The warning message needs to dereference al.map->dso...
> However, previous perf_event__preprocess_sample() doesn't always
> guarantee al.map != NULL, for example, when kernel map is restricted.
> 
> This patch validates al.map before dereferencing, avoid the segfault.
> 
> Before this patch:
> 
>  $ cat /proc/sys/kernel/kptr_restrict
>  1
>  $ perf top -p  120183

Thanks, applied.

- Arnaldo
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