• Jacob Wen's avatar
    l2tp: fix reading optional fields of L2TPv3 · 3924ebe5
    Jacob Wen authored
    [ Upstream commit 4522a70db7aa5e77526a4079628578599821b193 ]
    
    Use pskb_may_pull() to make sure the optional fields are in skb linear
    parts, so we can safely read them later.
    
    It's easy to reproduce the issue with a net driver that supports paged
    skb data. Just create a L2TPv3 over IP tunnel and then generates some
    network traffic.
    Once reproduced, rx err in /sys/kernel/debug/l2tp/tunnels will increase.
    
    Changes in v4:
    1. s/l2tp_v3_pull_opt/l2tp_v3_ensure_opt_in_linear/
    2. s/tunnel->version != L2TP_HDR_VER_2/tunnel->version == L2TP_HDR_VER_3/
    3. Add 'Fixes' in commit messages.
    
    Changes in v3:
    1. To keep consistency, move the code out of l2tp_recv_common.
    2. Use "net" instead of "net-next", since this is a bug fix.
    
    Changes in v2:
    1. Only fix L2TPv3 to make code simple.
       To fix both L2TPv3 and L2TPv2, we'd better refactor l2tp_recv_common.
       It's complicated to do so.
    2. Reloading pointers after pskb_may_pull
    
    Fixes: f7faffa3 ("l2tp: Add L2TPv3 protocol support")
    Fixes: 0d76751f ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support")
    Fixes: a32e0eec ("l2tp: introduce L2TPv3 IP encapsulation support for IPv6")
    Signed-off-by: 's avatarJacob Wen <jian.w.wen@oracle.com>
    Acked-by: 's avatarGuillaume Nault <gnault@redhat.com>
    Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    3924ebe5