| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 55/56] sched: Fix possible divide by zero in avg_atom() calculation | Date | Sat, 26 Jul 2014 12:02:48 -0700 |
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3.10-stable review patch. If anyone has any objections, please let me know.
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From: Mateusz Guzik <mguzik@redhat.com>
commit b0ab99e7736af88b8ac1b7ae50ea287fffa2badc upstream.
proc_sched_show_task() does:
if (nr_switches) do_div(avg_atom, nr_switches);
nr_switches is unsigned long and do_div truncates it to 32 bits, which means it can test non-zero on e.g. x86-64 and be truncated to zero for division.
Fix the problem by using div64_ul() instead.
As a side effect calculations of avg_atom for big nr_switches are now correct.
Signed-off-by: Mateusz Guzik <mguzik@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1402750809-31991-1-git-send-email-mguzik@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/sched/debug.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -551,7 +551,7 @@ void proc_sched_show_task(struct task_st avg_atom = p->se.sum_exec_runtime; if (nr_switches) - do_div(avg_atom, nr_switches); + avg_atom = div64_ul(avg_atom, nr_switches); else avg_atom = -1LL;
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