Add patch to fix integer overflow of points in oom_badness (rhbz 750402)

1 files changed, 100 insertions, 0 deletions

diff --git a/oom-fix-integer-overflow-of-points.patch b/oom-fix-integer-overflow-of-points.patch
new file mode 100644
index 000000000..02f6a8f72
--- /dev/null
+++ b/oom-fix-integer-overflow-of-points.patch
@@ -0,0 +1,100 @@
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+From:	Frantisek Hrbata <fhrbata@redhat.com>
+To:	rientjes@google.com
+Cc:	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
+	akpm@linux-foundation.org, kosaki.motohiro@jp.fujitsu.com,
+	oleg@redhat.com, minchan.kim@gmail.com, stable@kernel.org,
+	eteo@redhat.com, pmatouse@redhat.com
+Subject: [PATCH v2] oom: fix integer overflow of points in oom_badness
+Date:	Mon, 31 Oct 2011 16:56:09 +0100
+Message-Id: <1320076569-23872-1-git-send-email-fhrbata@redhat.com>
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+
+An integer overflow will happen on 64bit archs if task's sum of rss, swapents
+and nr_ptes exceeds (2^31)/1000 value. This was introduced by commit
+
+f755a04 oom: use pte pages in OOM score
+
+where the oom score computation was divided into several steps and it's no
+longer computed as one expression in unsigned long(rss, swapents, nr_pte are
+unsigned long), where the result value assigned to points(int) is in
+range(1..1000). So there could be an int overflow while computing
+
+176          points *= 1000;
+
+and points may have negative value. Meaning the oom score for a mem hog task
+will be one.
+
+196          if (points <= 0)
+197                  return 1;
+
+For example:
+[ 3366]     0  3366 35390480 24303939   5       0             0 oom01
+Out of memory: Kill process 3366 (oom01) score 1 or sacrifice child
+
+Here the oom1 process consumes more than 24303939(rss)*4096~=92GB physical
+memory, but it's oom score is one.
+
+In this situation the mem hog task is skipped and oom killer kills another and
+most probably innocent task with oom score greater than one.
+
+The points variable should be of type long instead of int to prevent the int
+overflow.
+
+Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com>
+---
+ mm/oom_kill.c |    2 +-
+ 1 files changed, 1 insertions(+), 1 deletions(-)
+
+diff --git a/mm/oom_kill.c b/mm/oom_kill.c
+index 626303b..e9a1785 100644
+--- a/mm/oom_kill.c
++++ b/mm/oom_kill.c
+@@ -162,7 +162,7 @@ static bool oom_unkillable_task(struct task_struct *p,
+ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
+ 		      const nodemask_t *nodemask, unsigned long totalpages)
+ {
+-	int points;
++	long points;
+ 
+ 	if (oom_unkillable_task(p, mem, nodemask))
+ 		return 0;
+-- 
+1.7.6.4
+
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