udp: disable gso with no_check_tx
Syzbot managed to send a udp gso packet without checksum offload into
the gso stack by disabling tx checksum (UDP_NO_CHECK6_TX). This
triggered the skb_warn_bad_offload.
RIP: 0010:skb_warn_bad_offload+0x2bc/0x600 net/core/dev.c:2658
skb_gso_segment include/linux/netdevice.h:4038 [inline]
validate_xmit_skb+0x54d/0xd90 net/core/dev.c:3120
__dev_queue_xmit+0xbf8/0x34c0 net/core/dev.c:3577
dev_queue_xmit+0x17/0x20 net/core/dev.c:3618
UDP_NO_CHECK6_TX sets skb->ip_summed to CHECKSUM_NONE just after the
udp gso integrity checks in udp_(v6_)send_skb. Extend those checks to
catch and fail in this case.
After the integrity checks jump directly to the CHECKSUM_PARTIAL case
to avoid reading the no_check_tx flags again (a TOCTTOU race).
Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 794aeaf..dd3102a 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -786,11 +786,14 @@
return -EINVAL;
if (skb->len > cork->gso_size * UDP_MAX_SEGMENTS)
return -EINVAL;
+ if (sk->sk_no_check_tx)
+ return -EINVAL;
if (skb->ip_summed != CHECKSUM_PARTIAL || is_udplite)
return -EIO;
skb_shinfo(skb)->gso_size = cork->gso_size;
skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
+ goto csum_partial;
}
if (is_udplite) /* UDP-Lite */
@@ -802,6 +805,7 @@
goto send;
} else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
+csum_partial:
udp4_hwcsum(skb, fl4->saddr, fl4->daddr);
goto send;