4.16-stable review patch. If anyone has any objections, please let me know.
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From: Michal Hocko mhocko@suse.com
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@kernel.org Reported-by: syzbot+8a5de3cce7cdc70e9ebe@syzkaller.appspotmail.com Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure") Signed-off-by: Michal Hocko mhocko@suse.com Reviewed-by: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Johannes Weiner hannes@cmpxchg.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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); }