linux-kernel - [25/68] sched: Fix user time incorrectly accounted as system time on 32-bit

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Date:	Fri, 24 Sep 2010 09:31:49 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: [25/68] sched: Fix user time incorrectly accounted as system time on 32-bit

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Stanislaw Gruszka <sgruszka@...hat.com>

commit e75e863dd5c7d96b91ebbd241da5328fc38a78cc upstream.

We have 32-bit variable overflow possibility when multiply in
task_times() and thread_group_times() functions. When the
overflow happens then the scaled utime value becomes erroneously
small and the scaled stime becomes i erroneously big.

Reported here:

 https://bugzilla.redhat.com/show_bug.cgi?id=633037
 https://bugzilla.kernel.org/show_bug.cgi?id=16559

Reported-by: Michael Chapman <redhat-bugzilla@...y.puzzling.org>
Reported-by: Ciriaco Garcia de Celis <sysman@...erpilot.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
LKML-Reference: <20100914143513.GB8415@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/sched.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5341,9 +5341,9 @@ void thread_group_times(struct task_stru
 	rtime = nsecs_to_cputime(cputime.sum_exec_runtime);
 
 	if (total) {
-		u64 temp;
+		u64 temp = rtime;
 
-		temp = (u64)(rtime * cputime.utime);
+		temp *= cputime.utime;
 		do_div(temp, total);
 		utime = (cputime_t)temp;
 	} else


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