• James Chapman's avatar
    l2tp: prevent possible tunnel refcount underflow · 24256415
    James Chapman authored
    When a session is created, it sets a backpointer to its tunnel. When
    the session refcount drops to 0, l2tp_session_free drops the tunnel
    refcount if session->tunnel is non-NULL. However, session->tunnel is
    set in l2tp_session_create, before the tunnel refcount is incremented
    by l2tp_session_register, which leaves a small window where
    session->tunnel is non-NULL when the tunnel refcount hasn't been
    bumped.
    
    Moving the assignment to l2tp_session_register is trivial but
    l2tp_session_create calls l2tp_session_set_header_len which uses
    session->tunnel to get the tunnel's encap. Add an encap arg to
    l2tp_session_set_header_len to avoid using session->tunnel.
    
    If l2tpv3 sessions have colliding IDs, it is possible for
    l2tp_v3_session_get to race with l2tp_session_register and fetch a
    session which doesn't yet have session->tunnel set. Add a check for
    this case.
    Signed-off-by: default avatarJames Chapman <jchapman@katalix.com>
    Signed-off-by: default avatarTom Parkin <tparkin@katalix.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    24256415
l2tp_core.h 10.9 KB