[PATCH net v2 2/3] net/packet: fix overflow in check for tp_frame_nr

[Andrey Konovalov]

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 <andreyk...@google.com>
---
 net/packet/af_packet.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 2323ee35dc09..3ac286ebb2f4 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4205,6 +4205,8 @@ 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;
-- 
2.12.2.564.g063fe858b8-goog