netdev - [PATCH 4/5] net/packet: fix overflow in check for tp

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Date:   Tue, 28 Mar 2017 16:00:48 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Craig Gallek <cgallek@...gle.com>
Cc:     netdev@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH 4/5] net/packet: fix overflow in check for tp_reserve

When calculating po->tp_hdrlen + po->tp_reserve the result can overflow.

Fix by checking that tp_reserve <= INT_MAX on assign.

This also takes cared of an overflow when calculating
 macoff = TPACKET_ALIGN(po->tp_hdrlen) + 16 + po->tp_reserve
 snaplen = skb->len
 macoff + snaplen
since macoff ~ INT_MAX and snaplen < SKB_MAX_ALLOC.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 net/packet/af_packet.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index c5c43fff8c01..28b49749d1af 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3665,6 +3665,8 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
 			return -EBUSY;
 		if (copy_from_user(&val, optval, sizeof(val)))
 			return -EFAULT;
+		if (val > INT_MAX)
+			return -EINVAL;
 		po->tp_reserve = val;
 		return 0;
 	}
@@ -4200,6 +4202,8 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 		if (unlikely((u64)req->tp_block_size * req->tp_block_nr >
 					UINT_MAX))
 			goto out;
+		if (unlikely(po->tp_reserve >= req->tp_frame_size))
+			goto out;
 
 		if (unlikely(!PAGE_ALIGNED(req->tp_block_size)))
 			goto out;
@@ -4207,9 +4211,6 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 		    req->tp_block_size <=
 			  BLK_PLUS_PRIV((u64)req_u->req3.tp_sizeof_priv))
 			goto out;
-		if (unlikely(req->tp_frame_size < po->tp_hdrlen +
-					po->tp_reserve))
-			goto out;
 		if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
 			goto out;
 
-- 
2.12.2.564.g063fe858b8-goog