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

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Date:	Wed, 15 Sep 2010 10:01:31 GMT
From:	tip-bot for Stanislaw Gruszka <sgruszka@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	seto.hidetoshi@...fujitsu.com, a.p.zijlstra@...llo.nl,
	redhat-bugzilla@...y.puzzling.org, sysman@...erpilot.com,
	tglx@...utronix.de, sgruszka@...hat.com, mingo@...e.hu
Subject: [tip:sched/urgent] sched: Fix user time incorrectly accounted as system time on 32-bit

Commit-ID:  e75e863dd5c7d96b91ebbd241da5328fc38a78cc
Gitweb:     http://git.kernel.org/tip/e75e863dd5c7d96b91ebbd241da5328fc38a78cc
Author:     Stanislaw Gruszka <sgruszka@...hat.com>
AuthorDate: Tue, 14 Sep 2010 16:35:14 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 15 Sep 2010 10:41:36 +0200

sched: Fix user time incorrectly accounted as system time on 32-bit

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>
Cc: <stable@...nel.org>  # 2.6.32.19+ (partially) and 2.6.33+
LKML-Reference: <20100914143513.GB8415@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index ed09d4f..dc85ceb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3513,9 +3513,9 @@ void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 	rtime = nsecs_to_cputime(p->se.sum_exec_runtime);
 
 	if (total) {
-		u64 temp;
+		u64 temp = rtime;
 
-		temp = (u64)(rtime * utime);
+		temp *= utime;
 		do_div(temp, total);
 		utime = (cputime_t)temp;
 	} else
@@ -3546,9 +3546,9 @@ void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 	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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