itimers: Fix racy writes to cpu_itimer fields

8747d793 · Stanislaw Gruszka <[email protected]> · 2009-11-17 14:14:12 -08:00

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 <[email protected]>
LKML-Reference: <[email protected]> 
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>

Commit: 8747d793fc5c4d3e4decd41d55f6dc24498dd5f5
Parents: 0696b711

Changes

1 files changed · +5 −2

File	Status	Add	Del	Content
kernel/itimer.c	modified	+5	−2	View file

kernel/itimer.c

View file

diff --git a/kernel/itimer.c b/kernel/itimer.c
index b03451e..d802883 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);
 