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Commit 09c37a2c authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

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: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 019ded3a

net/core/filter.c

+6 −6
Original line number Diff line number Diff line
@@ -2069,9 +2069,6 @@ 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):
@@ -2079,6 +2076,7 @@ static bool tc_cls_act_is_valid_access(int off, int size, 
		case offsetof(struct __sk_buff, priority):

		case offsetof(struct __sk_buff, cb[0]) ...

		     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);

		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):