• Xie He's avatar
    net: lapb: Copy the skb before sending a packet · 88c7a9fd
    Xie He authored
    When sending a packet, we will prepend it with an LAPB header.
    This modifies the shared parts of a cloned skb, so we should copy the
    skb rather than just clone it, before we prepend the header.
    
    In "Documentation/networking/driver.rst" (the 2nd point), it states
    that drivers shouldn't modify the shared parts of a cloned skb when
    transmitting.
    
    The "dev_queue_xmit_nit" function in "net/core/dev.c", which is called
    when an skb is being sent, clones the skb and sents the clone to
    AF_PACKET sockets. Because the LAPB drivers first remove a 1-byte
    pseudo-header before handing over the skb to us, if we don't copy the
    skb before prepending the LAPB header, the first byte of the packets
    received on AF_PACKET sockets can be corrupted.
    
    Fixes: 1da177e4 ("Linux-2.6.12-rc2")
    Signed-off-by: default avatarXie He <xie.he.0141@gmail.com>
    Acked-by: default avatarMartin Schiller <ms@dev.tdt.de>
    Link: https://lore.kernel.org/r/20210201055706.415842-1-xie.he.0141@gmail.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
    88c7a9fd
lapb_out.c 4.69 KB