• Christoph Schulz's avatar
    net: ppp: fix creating PPP pass and active filters · cc25eaae
    Christoph Schulz authored
    Commit 568f194e ("net: ppp: use
    sk_unattached_filter api") inadvertently changed the logic when setting
    PPP pass and active filters. This applies to both the generic PPP subsystem
    implemented by drivers/net/ppp/ppp_generic.c and the ISDN PPP subsystem
    implemented by drivers/isdn/i4l/isdn_ppp.c. The original code in ppp_ioctl()
    (or isdn_ppp_ioctl(), resp.) handling PPPIOCSPASS and PPPIOCSACTIVE allowed to
    remove a pass/active filter previously set by using a filter of length zero.
    However, with the new code this is not possible anymore as this case is not
    explicitly checked for, which leads to passing NULL as a filter to
    sk_unattached_filter_create(). This results in returning EINVAL to the caller.
    
    Additionally, the variables ppp->pass_filter and ppp->active_filter (or
    is->pass_filter and is->active_filter, resp.) are not reset to NULL, although
    the filters they point to may have been destroyed by
    sk_unattached_filter_destroy(), so in this EINVAL case dangling pointers are
    left behind (provided the pointers were previously non-NULL).
    
    This patch corrects both problems by checking whether the filter passed is
    empty or non-empty, and prevents sk_unattached_filter_create() from being
    called in the first case. Moreover, the pointers are always reset to NULL
    as soon as sk_unattached_filter_destroy() returns.
    Signed-off-by: default avatarChristoph Schulz <develop@kristov.de>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    cc25eaae
isdn_ppp.c 78.5 KB