net/packet: fix overflow in check for tp_frame_nr

Orabug: 25813773
CVE: CVE-2017-7308

When calculating rb->frames_per_block * req->tp_block_nr the result
can overflow.

Add a check that tp_block_size * tp_block_nr <= UINT_MAX.

Since frames_per_block <= tp_block_size, the expression would
never overflow.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 8f8d28e4d6d815a391285e121c3a53a0b6cb9e7b)
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 4b1bc45290045da67fd4831f92fd5d3d002919ba..cd4af1d1a58cad631e71e535a44919cad4f135e6 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3878,6 +3878,8 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
                rb->frames_per_block = req->tp_block_size/req->tp_frame_size;
                if (unlikely(rb->frames_per_block <= 0))
                        goto out;
+               if (unlikely(req->tp_block_size > UINT_MAX / req->tp_block_nr))
+                       goto out;
                if (unlikely((rb->frames_per_block * req->tp_block_nr) !=
                                        req->tp_frame_nr))
                        goto out;