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authorDaniel Borkmann <daniel@iogearbox.net>2018-10-24 22:05:45 +0200
committerAlexei Starovoitov <ast@kernel.org>2018-10-25 17:02:06 -0700
commit5d66fa7d9e9e9399ddfdc530f352dd6f7c724485 (patch)
treeda484f108d8b91eb463623140b1e9a497da3a94f /kernel
parentab21c1b5f799395232b838e98981cfed6d647905 (diff)
downloadlinux-5d66fa7d9e9e9399ddfdc530f352dd6f7c724485.tar.bz2
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 <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Cc: Petar Penkov <ppenkov@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 98fa0be35370..b0cc8f2ff95f 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;