[patch 2/5] oom: fix possible android low memory killer NULLpointer

[David Rientjes]

get_mm_rss() atomically dereferences the actual without checking for a
NULL pointer, which is possible since task_lock() is not held.

Cc: San Mehat <san@xxxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
 drivers/staging/android/lowmemorykiller.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -80,12 +80,18 @@ static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
 	for_each_process(p) {
 		int oom_adj;
 
-		if (!p->mm)
+		task_lock(p);
+		if (!p->mm) {
+			task_unlock(p);
 			continue;
+		}
 		oom_adj = p->oomkilladj;
-		if (oom_adj < 0)
+		if (oom_adj < 0) {
+			task_unlock(p);
 			continue;
+		}
 		tasksize = get_mm_rss(p->mm);
+		task_unlock(p);
 		if (nr_to_scan > 0 && tasksize > 0) {
 			if (!selected || oom_adj > selected_oom_adj ||
 			    (oom_adj == selected_oom_adj &&
--
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