mm: memcg: use proper memcg in limit bypass

Commit 84235de ("fs: buffer: move allocation failure loop into the allocator") allowed __GFP_NOFAIL allocations to bypass the limit if they fail to reclaim enough memory for the charge. But because the main test case was on a 3.2-based system, the patch missed the fact that on newer kernels the charge function needs to return root_mem_cgroup when bypassing the limit, and not NULL. This will corrupt whatever memory is at NULL + percpu pointer offset. Fix this quickly before problems are reported. Signed-off-by: Johannes Weiner <[email protected]> Acked-by: Michal Hocko <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
levisjani · Oct 31, 2013 · 3168ecb · 3168ecb
1 parent 12aee27
commit 3168ecb
Showing 1 changed file with 4 additions and 4 deletions.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
@@ -2765,10 +2765,10 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
 	*ptr = memcg;
 	return 0;
 nomem:
-	*ptr = NULL;
-	if (gfp_mask & __GFP_NOFAIL)
-		return 0;
-	return -ENOMEM;
+	if (!(gfp_mask & __GFP_NOFAIL)) {
+		*ptr = NULL;
+		return -ENOMEM;
+	}
 bypass:
 	*ptr = root_mem_cgroup;
 	return -EINTR;