• Daniel Borkmann's avatar
    net: cls_bpf: fix size mismatch on filter preparation · 7913ecf6
    Daniel Borkmann authored
    In cls_bpf_modify_existing(), we read out the number of filter blocks,
    do some sanity checks, allocate a block on that size, and copy over the
    BPF instruction blob from user space, then pass everything through the
    classic BPF checker prior to installation of the classifier.
    
    We should reject mismatches here, there are 2 scenarios: the number of
    filter blocks could be smaller than the provided instruction blob, so
    we do a partial copy of the BPF program, and thus the instructions will
    either be rejected from the verifier or a valid BPF program will be run;
    in the other case, we'll end up copying more than we're supposed to,
    and most likely the trailing garbage will be rejected by the verifier
    as well (i.e. we need to fit instruction pattern, ret {A,K} needs to be
    last instruction, load/stores must be correct, etc); in case not, we
    would leak memory when dumping back instruction patterns. The code should
    have only used nla_len() as Dave noted to avoid this from the beginning.
    Anyway, lets fix it by rejecting such load attempts.
    
    Fixes: 7d1d65cb ("net: sched: cls_bpf: add BPF-based classifier")
    Signed-off-by: default avatarDaniel Borkmann <dborkman@redhat.com>
    Acked-by: default avatarJiri Pirko <jiri@resnulli.us>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    7913ecf6
cls_bpf.c 8.21 KB