From 09c37a2c5bbc28b5fbc07a01db4bccdbd0a5d8a2 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 16 Mar 2016 01:42:49 +0100 Subject: [PATCH] bpf: make skb->tc_classid also readable Currently, the tc_classid from eBPF skb context is write-only, but there's no good reason for tc programs to limit it to write-only. For example, it can be used to transfer its state via tail calls where the resulting tc_classid gets filled gradually. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- net/core/filter.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 6fc3893a6170..69c7b2fecf44 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2069,16 +2069,14 @@ static bool sk_filter_is_valid_access(int off, int size, static bool tc_cls_act_is_valid_access(int off, int size, enum bpf_access_type type) { - if (off == offsetof(struct __sk_buff, tc_classid)) - return type == BPF_WRITE ? true : false; - if (type == BPF_WRITE) { switch (off) { case offsetof(struct __sk_buff, mark): case offsetof(struct __sk_buff, tc_index): case offsetof(struct __sk_buff, priority): case offsetof(struct __sk_buff, cb[0]) ... - offsetof(struct __sk_buff, cb[4]): + offsetof(struct __sk_buff, cb[4]): + case offsetof(struct __sk_buff, tc_classid): break; default: return false; @@ -2195,8 +2193,10 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg, ctx_off -= offsetof(struct __sk_buff, tc_classid); ctx_off += offsetof(struct sk_buff, cb); ctx_off += offsetof(struct qdisc_skb_cb, tc_classid); - WARN_ON(type != BPF_WRITE); - *insn++ = BPF_STX_MEM(BPF_H, dst_reg, src_reg, ctx_off); + if (type == BPF_WRITE) + *insn++ = BPF_STX_MEM(BPF_H, dst_reg, src_reg, ctx_off); + else + *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg, ctx_off); break; case offsetof(struct __sk_buff, tc_index): -- 2.34.1