CVE-2011-4097: Integer Overflow

https://lkml.org/lkml/2011/10/31/138 An integer overflow will happen on 64bit archs if task's sum of rss, swapents and nrptes 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, nrpte 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> --- mm/oomkill.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/mm/oomkill.c b/mm/oomkill.c index 626303b..e9a1785 100644 --- a/mm/oomkill.c +++ b/mm/oomkill.c @@ -162,7 +162,7 @@ static bool oomunkillabletask(struct taskstruct p, unsigned int oombadness(struct taskstruct p, struct memcgroup mem, const nodemaskt nodemask, unsigned long totalpages) { - int points; + long points; if (oomunkillabletask(p, mem, nodemask)) return 0;

Introduced by: http://git.kernel.org/linus/f755a04

Upstream commit: TBD

Acknowledgements:

Red Hat would like to thank Shubham Goyal for reporting this issue.