From: Daniel Borkmann Date: Wed, 24 Oct 2018 20:05:45 +0000 (+0200) Subject: bpf: fix direct packet access for flow dissector progs X-Git-Tag: v5.4-rc1~2332^2~6^2~2^2~4 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5d66fa7d9e9e9399ddfdc530f352dd6f7c724485;p=platform%2Fkernel%2Flinux-rpi.git bpf: fix direct packet access for flow dissector progs Commit d58e468b1112 ("flow_dissector: implements flow dissector BPF hook") added direct packet access for skbs in may_access_direct_pkt_data() function where this enables read and write access to the skb->data. This is buggy because without a prologue generator such as bpf_unclone_prologue() we would allow for writing into cloned skbs. Original intention might have been to only allow read access where this is not needed (similar as the flow_dissector_func_proto() indicates which enables only bpf_skb_load_bytes() as well), therefore this patch fixes it to restrict to read-only. Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook") Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Cc: Petar Penkov Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 98fa0be..b0cc8f2 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1387,21 +1387,23 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env, enum bpf_access_type t) { switch (env->prog->type) { + /* Program types only with direct read access go here! */ case BPF_PROG_TYPE_LWT_IN: case BPF_PROG_TYPE_LWT_OUT: case BPF_PROG_TYPE_LWT_SEG6LOCAL: case BPF_PROG_TYPE_SK_REUSEPORT: - /* dst_input() and dst_output() can't write for now */ + case BPF_PROG_TYPE_FLOW_DISSECTOR: if (t == BPF_WRITE) return false; /* fallthrough */ + + /* Program types with direct read + write access go here! */ case BPF_PROG_TYPE_SCHED_CLS: case BPF_PROG_TYPE_SCHED_ACT: case BPF_PROG_TYPE_XDP: case BPF_PROG_TYPE_LWT_XMIT: case BPF_PROG_TYPE_SK_SKB: case BPF_PROG_TYPE_SK_MSG: - case BPF_PROG_TYPE_FLOW_DISSECTOR: if (meta) return meta->pkt_access;