ARM: net: fix vlan access instructions in ARM JIT.

This makes BPF_ANC | SKF_AD_VLAN_TAG and BPF_ANC | SKF_AD_VLAN_TAG_PRESENT
have the same behaviour as the in kernel VM and makes the test_bpf LD_VLAN_TAG
and LD_VLAN_TAG_PRESENT tests pass.

Signed-off-by: Nicolas Schichan <nschichan@freebox.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index d9b25242f743..c011e2296cb1 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -889,9 +889,11 @@ b_epilogue:
                         off = offsetof(struct sk_buff, vlan_tci);
                         emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
                         if (code == (BPF_ANC | SKF_AD_VLAN_TAG))
-                                OP_IMM3(ARM_AND, r_A, r_A, VLAN_VID_MASK, ctx);
-                        else
-                                OP_IMM3(ARM_AND, r_A, r_A, VLAN_TAG_PRESENT, ctx);
+                                OP_IMM3(ARM_AND, r_A, r_A, ~VLAN_TAG_PRESENT, ctx);
+                        else {
+                                OP_IMM3(ARM_LSR, r_A, r_A, 12, ctx);
+                                OP_IMM3(ARM_AND, r_A, r_A, 0x1, ctx);
+                        }
                         break;
                 case BPF_ANC | SKF_AD_QUEUE:
                         ctx->seen |= SEEN_SKB;