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| author | Willem de Bruijn <willemb@google.com> | 2018-05-11 13:24:25 -0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-05-13 20:19:27 -0400 |
| commit | b84bbaf7a6c8cca24f8acf25a2c8e46913a947ba (patch) | |
| tree | bef9a144ff2af69bb75960f9c048d83b491201c1 /net/packet | |
| parent | 4bc871984f7cb5b2dec3ae64b570cb02f9ce2227 (diff) | |
| download | lwn-b84bbaf7a6c8cca24f8acf25a2c8e46913a947ba.tar.gz lwn-b84bbaf7a6c8cca24f8acf25a2c8e46913a947ba.zip | |
packet: in packet_snd start writing at link layer allocation
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>
Diffstat (limited to 'net/packet')
| -rw-r--r-- | net/packet/af_packet.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 01f3515cada0..e9422fe45179 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2903,13 +2903,15 @@ 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 */ |