[PATCH] oom: handle overflow in mem_cgroup_out_of_memory()

[Greg Thelen <gthelen@google.com>]

mem_cgroup_get_limit() returns a byte limit as a unsigned 64 bit value,
which is converted to a page count by mem_cgroup_out_of_memory().  Prior
to this patch the conversion could overflow on 32 bit platforms
yielding a limit of zero.

Signed-off-by: Greg Thelen <gthelen@google.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 7dcca55..3fcac51 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -538,7 +538,7 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
 	struct task_struct *p;
 
 	check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
-	limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT;
+	limit = min(mem_cgroup_get_limit(mem) >> PAGE_SHIFT, (u64)ULONG_MAX);
 	read_lock(&tasklist_lock);
 retry:
 	p = select_bad_process(&points, limit, mem, NULL);
-- 
1.7.3.1