memcg: fix oops in mem_cgroup_shrink_usage

Got an oops in mem_cgroup_shrink_usage() when testing loop over tmpfs: yes, of course, loop0 has no mm: other entry points check but this didn't. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

memcg: fix oops in mem_cgroup_shrink_usage
Got an oops in mem_cgroup_shrink_usage() when testing loop over tmpfs: yes, of course, loop0 has no mm: other entry points check but this didn't. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hugh Dickins · Linus Torvalds
1 parent 3ee1062b4e
Showing 1 changed file with 2 additions and 0 deletions Side-by-side Diff
mm/memcontrol.c
@@ -796,6 +796,8 @@
  
 	if (mem_cgroup_subsys.disabled)
 		return 0;
+	if (!mm)
+		return 0;
  
 	rcu_read_lock();
 	mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
...	...	@@ -796,6 +796,8 @@
796	796
797	797	if (mem_cgroup_subsys.disabled)
798	798	return 0;
	799	+ if (!mm)
	800	+ return 0;
799	801
800	802	rcu_read_lock();
801	803	mem = mem_cgroup_from_task(rcu_dereference(mm->owner));