summaryrefslogtreecommitdiff
path: root/net/packet
diff options
context:
space:
mode:
authorWillem de Bruijn <willemb@google.com>2018-05-11 13:24:25 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-25 16:12:55 +0200
commit6190cce26e40bf71c4d375b21eea74bb07b6a0f3 (patch)
tree9035a39d1cd4648b099788843395c3a972b011f2 /net/packet
parent2ef22bd08dcff6a8d761829647e5eb321576a83a (diff)
packet: in packet_snd start writing at link layer allocation
[ Upstream commit b84bbaf7a6c8cca24f8acf25a2c8e46913a947ba ] Packet sockets allow construction of packets shorter than dev->hard_header_len to accommodate protocols with variable length link layer headers. These packets are padded to dev->hard_header_len, because some device drivers interpret that as a minimum packet size. packet_snd reserves dev->hard_header_len bytes on allocation. SOCK_DGRAM sockets call skb_push in dev_hard_header() to ensure that link layer headers are stored in the reserved range. SOCK_RAW sockets do the same in tpacket_snd, but not in packet_snd. Syzbot was able to send a zero byte packet to a device with massive 116B link layer header, causing padding to cross over into skb_shinfo. Fix this by writing from the start of the llheader reserved range also in the case of packet_snd/SOCK_RAW. Update skb_set_network_header to the new offset. This also corrects it for SOCK_DGRAM, where it incorrectly double counted reserve due to the skb_push in dev_hard_header. Fixes: 9ed988cd5915 ("packet: validate variable length ll headers") Reported-by: syzbot+71d74a5406d02057d559@syzkaller.appspotmail.com Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/packet')
-rw-r--r--net/packet/af_packet.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index a027f8c00944..b2b50756263b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2910,13 +2910,15 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
if (skb == NULL)
goto out_unlock;
- skb_set_network_header(skb, reserve);
+ skb_reset_network_header(skb);
err = -EINVAL;
if (sock->type == SOCK_DGRAM) {
offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len);
if (unlikely(offset < 0))
goto out_free;
+ } else if (reserve) {
+ skb_push(skb, reserve);
}
/* Returns -EFAULT on error */