4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michal Hocko <mhocko@xxxxxxxx> commit 4eaf431f6f71bbed40a4c733ffe93a7e8cedf9d9 upstream. syzbot has triggered a NULL ptr dereference when allocation fault injection enforces a failure and alloc_mem_cgroup_per_node_info initializes memcg->nodeinfo only half way through. But __mem_cgroup_free still tries to free all per-node data and dereferences pn->lruvec_stat_cpu unconditioanlly even if the specific per-node data hasn't been initialized. The bug is quite unlikely to hit because small allocations do not fail and we would need quite some numa nodes to make struct mem_cgroup_per_node large enough to cross the costly order. Link: http://lkml.kernel.org/r/20180406100906.17790-1-mhocko@xxxxxxxxxx Reported-by: syzbot+8a5de3cce7cdc70e9ebe@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure") Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4108,6 +4108,9 @@ static void free_mem_cgroup_per_node_inf { struct mem_cgroup_per_node *pn = memcg->nodeinfo[node]; + if (!pn) + return; + free_percpu(pn->lruvec_stat_cpu); kfree(pn); }
