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

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Date:	Tue, 24 Aug 2010 08:02:22 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	kosaki.motohiro@...fujitsu.com, Xiaotian Feng <dfeng@...hat.com>,
	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>,
	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>
> 

Unfortunatelly, I have no time to review deeply this one. but I see my test
works. Also, I'd like to say I like this one.

Thanks.



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