patches/kernel/0007-net-packet-fix-overflow-in-tpacket_rcv.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Or Cohen <orcohen@paloaltonetworks.com>
   3 Date: Sun, 30 Aug 2020 20:04:51 +0300
   4 Subject: [PATCH] net/packet: fix overflow in tpacket_rcv
   5
   6 Using tp_reserve to calculate netoff can overflow as
   7 tp_reserve is unsigned int and netoff is unsigned short.
   8
   9 This may lead to macoff receving a smaller value then
  10 sizeof(struct virtio_net_hdr), and if po->has_vnet_hdr
  11 is set, an out-of-bounds write will occur when
  12 calling virtio_net_hdr_from_skb.
  13
  14 The bug is fixed by converting netoff to unsigned int
  15 and checking if it exceeds USHRT_MAX.
  16
  17 Fixes: 8913336a7e8d ("packet: add PACKET_RESERVE sockopt")
  18 Signed-off-by: Or Cohen <orcohen@paloaltonetworks.com>
  19 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  20 ---
  21  net/packet/af_packet.c | 7 ++++++-
  22  1 file changed, 6 insertions(+), 1 deletion(-)
  23
  24 diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
  25 index 7735340c892e..fbc2d4dfddf0 100644
  26 --- a/net/packet/af_packet.c
  27 +++ b/net/packet/af_packet.c
  28 @@ -2169,7 +2169,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
  29         int skb_len = skb->len;
  30         unsigned int snaplen, res;
  31         unsigned long status = TP_STATUS_USER;
  32 -       unsigned short macoff, netoff, hdrlen;
  33 +       unsigned short macoff, hdrlen;
  34 +       unsigned int netoff;
  35         struct sk_buff *copy_skb = NULL;
  36         struct timespec ts;
  37         __u32 ts_status;
  38 @@ -2238,6 +2239,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
  39                 }
  40                 macoff = netoff - maclen;
  41         }
  42 +       if (netoff > USHRT_MAX) {
  43 +               atomic_inc(&po->tp_drops);
  44 +               goto drop_n_restore;
  45 +       }
  46         if (po->tp_version <= TPACKET_V2) {
  47                 if (macoff + snaplen > po->rx_ring.frame_size) {
  48                         if (po->copy_thresh &&