task_numa_placement() oopsed on NULL p->mm when task_numa_fault()
got called in the handling of break_ksm() for ksmd. That might be a
peculiar case, which perhaps KSM could takes steps to avoid? but it's
more robust if task_numa_placement() allows for such a possibility.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
kernel/sched/fair.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- 3.7+git/kernel/sched/fair.c 2012-12-16 16:35:08.724441527 -0800
+++ linux/kernel/sched/fair.c 2012-12-18 21:37:24.727964195 -0800
@@ -793,8 +793,11 @@ unsigned int sysctl_numa_balancing_scan_
static void task_numa_placement(struct task_struct *p)
{
- int seq = ACCESS_ONCE(p->mm->numa_scan_seq);
+ int seq;
+ if (!p->mm) /* for example, ksmd faulting in a user's mm */
+ return;
+ seq = ACCESS_ONCE(p->mm->numa_scan_seq);
if (p->numa_scan_seq == seq)
return;
p->numa_scan_seq = seq;
--
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