Staging: android: lowmemorykiller: fix possible android low memory killer NULL pointer

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@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index f61333b9602..cba3b91d728 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -92,12 +92,18 @@ 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 < min_adj)
+                if (oom_adj < min_adj) {
+                        task_unlock(p);
                         continue;
+                }
                 tasksize = get_mm_rss(p->mm);
+                task_unlock(p);
                 if (tasksize <= 0)
                         continue;
                 if (selected) {