Messages in this thread Patch in this message | | | Date | Wed, 16 Jul 2014 12:22:10 -0700 | From | tip-bot for Mateusz Guzik <> | Subject | [tip:sched/urgent] sched: Fix possible divide by zero in avg_atom () calculation |
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Commit-ID: b0ab99e7736af88b8ac1b7ae50ea287fffa2badc Gitweb: http://git.kernel.org/tip/b0ab99e7736af88b8ac1b7ae50ea287fffa2badc Author: Mateusz Guzik <mguzik@redhat.com> AuthorDate: Sat, 14 Jun 2014 15:00:09 +0200 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 16 Jul 2014 13:36:07 +0200
sched: Fix possible divide by zero in avg_atom() calculation
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: stable@vger.kernel.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> --- kernel/sched/debug.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 695f977..627b3c3 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -608,7 +608,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m) 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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