linux-kernel - Re: [PATCH 2/2] perf tools: Fix fault in tracepoint_error if NULL is passed to parse

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Date:	Mon, 1 Feb 2016 10:53:29 +0200
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Wang Nan <wangnan0@...wei.com>, acme@...nel.org
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Tong Zhang <ztong@...edu>, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 2/2] perf tools: Fix fault in tracepoint_error if NULL is
 passed to parse_event

On 01/02/16 05:21, Wang Nan wrote:
> Following segfault can happen with a non-root user:
> 
>  $ ./perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
>  WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
>  check /proc/sys/kernel/kptr_restrict.
> 
>  Samples in kernel functions may not be resolved if a suitable vmlinux
>  file is not found in the buildid cache or in the vmlinux path.
> 
>  Samples in kernel modules won't be resolved at all.
> 
>  If some relocation was applied (e.g. kexec) symbols may be misresolved
>  even with a suitable vmlinux or kallsyms file.
> 
>  Segmentation fault (core dumped)
> 
> The error is in tracepoint_error: it assumes 'e' is valid.
> 
> However, there are many situation a parse_event can be called without
> parse_events_error. See result of
> 'grep 'parse_events(.*NULL)' ./tools/perf/ -r'.
> 
> This patch makes tracepoint_error() directly return when !e.

I sent the same fix here:

	http://marc.info/?l=linux-kernel&m=145381056111871

> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Tong Zhang <ztong@...edu>
> Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> ---
>  tools/perf/util/parse-events.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 4f7b0ef..813d9b2 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -399,6 +399,9 @@ static void tracepoint_error(struct parse_events_error *e, int err,
>  {
>  	char help[BUFSIZ];
>  
> +	if (!e)
> +		return;
> +
>  	/*
>  	 * We get error directly from syscall errno ( > 0),
>  	 * or from encoded pointer's error ( < 0).
>