The skb->pkt_type field is defined as follows:
u8 pkt_type:3,
fclone:2,
ipvs_property:1,
peeked:1,
nf_trace:1
resulting to the following layout in big-endian systems
[pkt_type][fclone][ipvs_propery][peeked][nf_trace]
^ ^
| |
LSB MSB
As a result, the existing code did not work because it was trying to
match pkt_type == 7 whereas in reality it is 7<<5 on big-endian
systems.
This has been fixed in the interpreter in
0dcceabb0c1bf2d4c12a748df9933fad303072a7
"net: filter: fix SKF_AD_PKTTYPE extension on big-endian"
The fix is to look for 7<<5 on big-endian systems for the pkt_type
field, and shift by 5 so the packet type will be at the lower 3 bits
of the A register.
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Daniel Borkmann <dborkman@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
---
arch/mips/net/bpf_jit.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 09ebc886c7aa..4920e0fd05ee 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -745,13 +745,17 @@ static u64 jit_get_skb_w(struct sk_buff *skb, unsigned offset)
return (u64)err << 32 | ntohl(ret);
}
-#define PKT_TYPE_MAX 7
+#ifdef __BIG_ENDIAN_BITFIELD
+#define PKT_TYPE_MAX (7 << 5)
+#else
+#define PKT_TYPE_MAX 7
+#endif
static int pkt_type_offset(void)
{
struct sk_buff skb_probe = {
.pkt_type = ~0,
};
- char *ct = (char *)&skb_probe;
+ u8 *ct = (u8 *)&skb_probe;
unsigned int off;
for (off = 0; off < sizeof(struct sk_buff); off++) {
@@ -1314,6 +1318,10 @@ jmp_cmp:
emit_load_byte(r_tmp, r_skb, off, ctx);
/* Keep only the last 3 bits */
emit_andi(r_A, r_tmp, PKT_TYPE_MAX, ctx);
+#ifdef __BIG_ENDIAN_BITFIELD
+ /* Get the actual packet type to the lower 3 bits */
+ emit_srl(r_A, r_A, 5, ctx);
+#endif
break;
case BPF_ANC | SKF_AD_QUEUE:
ctx->flags |= SEEN_SKB | SEEN_A;
--
2.0.0
