linux-kernel - [PATCH AUTOSEL for 4.9 41/50] sched/cputime, powerpc32: Fix stale scaled stime on context switch

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 25 Oct 2017 01:56:02 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Frederic Weisbecker <fweisbec@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Ingo Molnar <mingo@...nel.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH AUTOSEL for 4.9 41/50] sched/cputime, powerpc32: Fix stale
 scaled stime on context switch

From: Frederic Weisbecker <fweisbec@...il.com>

[ Upstream commit 90d08ba2b9b4be4aeca6a5b5a4b09fbcde30194d ]

On context switch with powerpc32, the cputime is accumulated in the
thread_info struct. So the switching-in task must move forward its
start time snapshot to the current time in order to later compute the
delta spent in system mode.

This is what we do for the normal cputime by initializing the starttime
field to the value of the previous task's starttime which got freshly
updated.

But we are missing the update of the scaled cputime start time. As a
result we may be accounting too much scaled cputime later.

Fix this by initializing the scaled cputime the same way we do for
normal cputime.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Christian Borntraeger <borntraeger@...ibm.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Stanislaw Gruszka <sgruszka@...hat.com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Wanpeng Li <wanpeng.li@...mail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 arch/powerpc/kernel/time.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index bc3f7d0d7b79..f1d7e996e673 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -407,6 +407,7 @@ void arch_vtime_task_switch(struct task_struct *prev)
 	struct cpu_accounting_data *acct = get_accounting(current);
 
 	acct->starttime = get_accounting(prev)->starttime;
+	acct->startspurr = get_accounting(prev)->startspurr;
 	acct->system_time = 0;
 	acct->user_time = 0;
 }
-- 
2.11.0