If kernel booted with cgroup_disabl=memory, the memcg in mem_cgroup_swappiness() could be NULL. Derefernce memcg only if mem_cgroup_disabled() = false, otherwise:
BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff8122d6cc>] mem_cgroup_swappiness+0xc/0x30 RIP: 0010:[<ffffffff8122d6cc>] [<ffffffff8122d6cc>] mem_cgroup_swappiness+0xc/0x30 Call Trace: [<ffffffff811c195a>] balance_pgdat+0x4ca/0x820 [<ffffffff811c1e23>] kswapd+0x173/0x440 [<ffffffff810bf741>] kthread+0xd1/0xe0 [<ffffffff817556f7>] ret_from_fork_nospec_begin+0x21/0x21 https://pmc.acronis.com/browse/VSTOR-18694 Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com> --- mm/memcontrol.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c889102fe955..31ba8dcb6bc7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2033,10 +2033,8 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg, bool kmem) int mem_cgroup_swappiness(struct mem_cgroup *memcg) { - struct cgroup *cgrp = memcg->css.cgroup; - /* root ? */ - if (mem_cgroup_disabled() || cgrp->parent == NULL) + if (mem_cgroup_disabled() || memcg->css.cgroup->parent == NULL) return vm_swappiness; return memcg->swappiness; -- 2.19.2 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
