MIPS: bpf: Fix return values for VLAN_TAG_PRESENT case

If VLAN_TAG_PRESENT is not zero, then return 1 as expected by
classic BPF. Otherwise return 0.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: netdev@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7128/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index a4d1b76e7373..d852bb6d3fe3 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -1316,10 +1316,13 @@ jmp_cmp:
                                                   vlan_tci) != 2);
                         off = offsetof(struct sk_buff, vlan_tci);
                         emit_half_load(r_s0, r_skb, off, ctx);
-                        if (code == (BPF_ANC | SKF_AD_VLAN_TAG))
+                        if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
                                 emit_andi(r_A, r_s0, (u16)~VLAN_TAG_PRESENT, ctx);
-                        else
+                        } else {
                                 emit_andi(r_A, r_s0, VLAN_TAG_PRESENT, ctx);
+                                /* return 1 if present */
+                                emit_sltu(r_A, r_zero, r_A, ctx);
+                        }
                         break;
                 case BPF_ANC | SKF_AD_PKTTYPE:
                         ctx->flags |= SEEN_SKB;