• Willem de Bruijn's avatar
    udp: disable gso with no_check_tx · a8c744a8
    Willem de Bruijn authored
    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: bec1f6f6
    
     ("udp: generate gso with UDP_SEGMENT")
    Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    a8c744a8