The patch titled
Subject: mm: memcg: fix use after free in mem_cgroup_iter()
has been added to the -mm tree. Its filename is
mm-memcg-fix-use-after-free-in-mem_cgroup_iter.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-fix-use-after-free-in-mem_cgroup_iter.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-fix-use-after-free-in-mem_cgroup_iter.patch
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------------------------------------------------------
From: Jing Xia <jing.xia.mail@xxxxxxxxx>
Subject: mm: memcg: fix use after free in mem_cgroup_iter()
It was reported that a kernel crash happened in mem_cgroup_iter(), which
can be triggered if the legacy cgroup-v1 non-hierarchical mode is used.
Unable to handle kernel paging request at virtual address 6b6b6b6b6b6b8f
......
Call trace:
mem_cgroup_iter+0x2e0/0x6d4
shrink_zone+0x8c/0x324
balance_pgdat+0x450/0x640
kswapd+0x130/0x4b8
kthread+0xe8/0xfc
ret_from_fork+0x10/0x20
mem_cgroup_iter():
......
if (css_tryget(css)) <-- crash here
break;
......
The crashing reason is that mem_cgroup_iter() uses the memcg object whose
pointer is stored in iter->position, which has been freed before and
filled with POISON_FREE(0x6b).
And the root cause of the use-after-free issue is that
invalidate_reclaim_iterators() fails to reset the value of iter->position
to NULL when the css of the memcg is released in non- hierarchical mode.
Link: http://lkml.kernel.org/r/1531994807-25639-1-git-send-email-jing.xia@xxxxxxxxxx
Fixes: 6df38689e0e9 ("mm: memcontrol: fix possible memcg leak due to interrupted reclaim")
Signed-off-by: Jing Xia <jing.xia.mail@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: <chunyan.zhang@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN mm/memcontrol.c~mm-memcg-fix-use-after-free-in-mem_cgroup_iter mm/memcontrol.c
--- a/mm/memcontrol.c~mm-memcg-fix-use-after-free-in-mem_cgroup_iter
+++ a/mm/memcontrol.c
@@ -850,7 +850,7 @@ static void invalidate_reclaim_iterators
int nid;
int i;
- while ((memcg = parent_mem_cgroup(memcg))) {
+ for (; memcg; memcg = parent_mem_cgroup(memcg)) {
for_each_node(nid) {
mz = mem_cgroup_nodeinfo(memcg, nid);
for (i = 0; i <= DEF_PRIORITY; i++) {
_
Patches currently in -mm which might be from jing.xia.mail@xxxxxxxxx are
mm-memcg-fix-use-after-free-in-mem_cgroup_iter.patch
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