linux-kernel - Re: [tip:tracing/ftrace] kernel/trace/trace_functions_graph.c: fix nsecs

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Message-ID: <20090323164745.GB5988@nowhere>
Date:	Mon, 23 Mar 2009 17:47:46 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	rostedt@...dmis.org, tglx@...utronix.de, daniel@...aq.de,
	mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:tracing/ftrace] kernel/trace/trace_functions_graph.c: fix
	nsecs_str buffer size

On Mon, Mar 23, 2009 at 04:42:27PM +0000, Daniel Mack wrote:
> Commit-ID:  603b9b9081ae0a1af986b9059a0a5055876ddea9
> Gitweb:     http://git.kernel.org/tip/603b9b9081ae0a1af986b9059a0a5055876ddea9
> Author:     Daniel Mack <daniel@...aq.de>
> AuthorDate: Mon, 23 Mar 2009 17:10:37 +0100
> Committer:  Ingo Molnar <mingo@...e.hu>
> CommitDate: Mon, 23 Mar 2009 17:40:51 +0100
> 
> kernel/trace/trace_functions_graph.c: fix nsecs_str buffer size
> 
> Impact: fix currently inactive buffer-overflow
> 
> In kernel/trace/trace_functions_graph.c, print_graph_duration(),
> len can be as low as 1 or 2, which could make snprintf() write
> beyond the buffer bounds. (Found by cppcheck, no real-world bug
> occured)
> 
> Signed-off-by: Daniel Mack <daniel@...aq.de>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> LKML-Reference: <1237824637-28190-1-git-send-email-daniel@...aq.de>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> 
> 
> ---
>  kernel/trace/trace_functions_graph.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)



Ingo, as I explained to Daniel before (I should have Cc you),
there is no overflow to protect here, so this patch will not
change anything.

This is my bad, I should better comment my code.

Frederic.


 
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index e876816..a305472 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -430,7 +430,7 @@ print_graph_duration(unsigned long long duration, struct trace_seq *s)
>  	unsigned long nsecs_rem = do_div(duration, 1000);
>  	/* log10(ULONG_MAX) + '\0' */
>  	char msecs_str[21];
> -	char nsecs_str[5];
> +	char nsecs_str[8];
>  	int ret, len;
>  	int i;
>  

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