[PATCH 4/5] net/packet: fix overflow in check for tp_reserve

[Andrey Konovalov]

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 <andreyk...@google.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