linux-kernel - [patch 4/7] oom: fix possible android low memory killer NULL pointer

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Date:	Mon, 4 May 2009 17:26:59 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
cc:	Nick Piggin <npiggin@...e.de>, San Mehat <san@...roid.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	linux-kernel@...r.kernel.org
Subject: [patch 4/7] oom: 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@...roid.com>
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 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
@@ -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) {
--
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