From 8747d793fc5c4d3e4decd41d55f6dc24498dd5f5 Mon Sep 17 00:00:00 2001
From: Stanislaw Gruszka <sgruszka@redhat.com>
Date: Tue, 17 Nov 2009 14:14:12 -0800
Subject: itimers: Fix racy writes to cpu_itimer fields
incr_error and error fields of struct cpu_itimer are used when calculating
next timer tick in check_cpu_itimers() and should not be modified without
tsk->sighand->siglock taken.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
LKML-Reference: <1253802903-979-1-git-send-email-sgruszka@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/itimer.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/itimer.c b/kernel/itimer.c
index b03451ede52..d802883153d 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -146,6 +146,7 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
{
cputime_t cval, nval, cinterval, ninterval;
s64 ns_ninterval, ns_nval;
+ u32 error, incr_error;
struct cpu_itimer *it = &tsk->signal->it[clock_id];
nval = timeval_to_cputime(&value->it_value);
@@ -153,8 +154,8 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
ninterval = timeval_to_cputime(&value->it_interval);
ns_ninterval = timeval_to_ns(&value->it_interval);
- it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
- it->error = cputime_sub_ns(nval, ns_nval);
+ error = cputime_sub_ns(nval, ns_nval);
+ incr_error = cputime_sub_ns(ninterval, ns_ninterval);
spin_lock_irq(&tsk->sighand->siglock);
@@ -168,6 +169,8 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
}
it->expires = nval;
it->incr = ninterval;
+ it->error = error;
+ it->incr_error = incr_error;
trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
--
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