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Commit 8747d793 authored by Stanislaw Gruszka's avatar Stanislaw Gruszka Committed by Thomas Gleixner
Browse files

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: default avatarStanislaw 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 0696b711

kernel/itimer.c

+5 −2
Original line number Diff line number Diff line
@@ -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);