linux-kernel - Re: [RFC PATCH v3] core_pattern: fix long parameters was truncated by core

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Date:	Mon, 23 Aug 2010 07:07:19 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Xiaotian Feng <dfeng@...hat.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Roland McGrath <roland@...hat.com>
Subject: Re: [RFC PATCH v3] core_pattern: fix long parameters was truncated
 by core_pattern handler

On Fri, Aug 20, 2010 at 05:35:58PM +0800, Xiaotian Feng wrote:
> We met a parameter truncated issue, consider following:
> > echo "|/root/core_pattern_pipe_test %p /usr/libexec/blah-blah-blah \
> %s %c %p %u %g 11 12345678901234567890123456789012345678 %t" > \
> /proc/sys/kernel/core_pattern
> 
> This is okay because the strings is less than CORENAME_MAX_SIZE.
> "cat /proc/sys/kernel/core_pattern" shows the whole string. but
> after we run core_pattern_pipe_test in man page, we found last
> parameter was truncated like below:
>         argc[10]=<12807486>
> 
> The root cause is core_pattern allows % specifiers, which need to be
> replaced during parse time, but the replace may expand the strings
> to larger than CORENAME_MAX_SIZE. So if the last parameter is %
> specifiers, the replace code is using snprintf(out_ptr, out_end - out_ptr, ...),
> this will write out of corename array.
> 
> Changes since v2:
> Introduced generic function cn_printf and make format_corename remember the time
> has been expanded.
> 
> Changes since v1:
> This patch allocates corename at runtime, if the replace doesn't have enough
> memory, expand the corename dynamically.
> 
> Signed-off-by: Xiaotian Feng <dfeng@...hat.com>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: Neil Horman <nhorman@...driver.com>
> Cc: Roland McGrath <roland@...hat.com>
> ---
>  fs/exec.c |  180 ++++++++++++++++++++++++++++++++++++++++--------------------
>  1 files changed, 120 insertions(+), 60 deletions(-)
> 
This looks alot cleaner.  Thanks!
Reviewed-by: Neil Horman <nhorman@...driver.com>

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