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CVE-2011-4097: oom: fix integer overflow of points in oom_badness · torvalds/linux@56c6a8a
Integer overflow in the oom_badness function in mm/oom_kill.c in the Linux kernel before 3.1.8 on 64-bit platforms allows local users to cause a denial of service (memory consumption or process termination) by using a certain large amount of memory.
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oom: fix integer overflow of points in oom_badness
commit ff05b6f upstream.
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 [email protected] Acked-by: KOSAKI Motohiro [email protected] Acked-by: Oleg Nesterov [email protected] Acked-by: David Rientjes [email protected] Signed-off-by: Andrew Morton [email protected] Signed-off-by: Linus Torvalds [email protected] Signed-off-by: Greg Kroah-Hartman [email protected]
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