linux-kernel - Re: [GIT PULL] oprofile fixes for 3.2

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Date:	Mon, 19 Dec 2011 15:00:49 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Robert Richter <robert.richter@....com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	oprofile-list <oprofile-list@...ts.sourceforge.net>
Subject: Re: [GIT PULL] oprofile fixes for 3.2


* Robert Richter <robert.richter@....com> wrote:

> Ingo,
> 
> please pull this one fix for 3.2.
> 
> Thanks,
> 
> -Robert
> 
> 
> 
> The following changes since commit dc47ce90c3a822cd7c9e9339fe4d5f61dcb26b50:
> 
>   Linux 3.2-rc5 (2011-12-09 15:09:32 -0800)
> 
> are available in the git repository at:
>   git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile.git urgent
> 
> Robert Richter (1):
>       oprofile: Fix uninitialized memory access when writing to oprofilefs
> 
>  arch/s390/oprofile/init.c         |    3 +++
>  drivers/oprofile/oprofile_files.c |    9 +++++++++
>  drivers/oprofile/oprofilefs.c     |   15 ++++++++++++++-
>  3 files changed, 26 insertions(+), 1 deletions(-)

Hm, i really don't like this:

+	if (!count)
+		return 0;
+
 	retval = oprofilefs_ulong_from_user(&val, buf, count);
 	if (retval)
 		return retval;

+	if (!count)
+		return 0;
+
 	retval = oprofilefs_ulong_from_user(&val, buf, count);
 	if (retval)
 		return retval;

+	if (!count)
+		return 0;
+
 	retval = oprofilefs_ulong_from_user(&val, buf, count);
 	if (retval)
 		return retval;
 
+	if (!count)
+		return 0;
+
 	retval = oprofilefs_ulong_from_user(&val, buf, count);
 	if (retval)
 		return retval;

+	if (!count)
+		return 0;
+
 	retval = oprofilefs_ulong_from_user(&value, buf, count);
 	if (retval)
 		return retval;

See the ugly and fragile pattern?

This should *really* be solved via the 
oprofilefs_ulong_from_user() helper function, not by sprinkling 
the !count checks in half a dozen places ...

Thanks,

	Ingo
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