From 7913ecf69e24bd7575e0d0325eda3b43c8cfa749 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Thu, 22 Jan 2015 10:41:01 +0100 Subject: 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: 7d1d65cb84e1 ("net: sched: cls_bpf: add BPF-based classifier") Signed-off-by: Daniel Borkmann Acked-by: Jiri Pirko Signed-off-by: David S. Miller --- net/sched/cls_bpf.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'net/sched') diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c index 84c8219c3e1c..49e5fa8795ae 100644 --- a/net/sched/cls_bpf.c +++ b/net/sched/cls_bpf.c @@ -180,6 +180,11 @@ static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp, } bpf_size = bpf_len * sizeof(*bpf_ops); + if (bpf_size != nla_len(tb[TCA_BPF_OPS])) { + ret = -EINVAL; + goto errout; + } + bpf_ops = kzalloc(bpf_size, GFP_KERNEL); if (bpf_ops == NULL) { ret = -ENOMEM; -- cgit v1.2.3