net: cls_bpf: fix size mismatch on filter preparation
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:Daniel Borkmann <dborkman@redhat.com> Acked-by:
Jiri Pirko <jiri@resnulli.us> Signed-off-by:
David S. Miller <davem@davemloft.net>
parent
9e79ce66
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