bpf: Fix integer overflow in queue_stack_map_alloc.

Integer overflow in queue_stack_map_alloc when calculating size may lead to heap overflow of arbitrary length. The patch fix it by checking whether attr->max_entries+1 < attr->max_entries and bailing out if it is the case. The vulnerability is discovered with the assistance of syzkaller.

To: Alexei Starovoitov <[email protected]>

---
 kernel/bpf/queue_stack_maps.c | 2 ++
 1 file changed, 2 insertions(+)

index 8bbd72d3a121..c35a8a4721c8 100644
@@ -67,6 +67,8 @@ static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
 	u64 queue_size, cost;
 
 	size = attr->max_entries + 1;
+	if (size < attr->max_entries)
+		return ERR_PTR(-EINVAL);
 	value_size = attr->value_size;
 
 	queue_size = sizeof(*qs) + (u64) value_size * size;

2.17.1