bpf: make sure to clear unused fields in tunnel/xfrm state fetch

Since the remaining bits are not filled in struct bpf_tunnel_key
resp. struct bpf_xfrm_state and originate from uninitialized stack
space, we should make sure to clear them before handing control
back to the program.

Also add a padding element to struct bpf_xfrm_state for future use
similar as we have in struct bpf_tunnel_key and clear it as well.

struct bpf_xfrm_state {
__u32 reqid; /* 0 4 */
__u32 spi; /* 4 4 */
__u16 family; /* 8 2 */

/* XXX 2 bytes hole, try to pack */

union {
__u32 remote_ipv4; /* 4 */
__u32 remote_ipv6[4]; /* 16 */
}; /* 12 16 */

/* size: 28, cachelines: 1, members: 4 */
/* sum members: 26, holes: 1, sum holes: 2 */
/* last cacheline: 28 bytes */
};

Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Alexei Starovoitov <[e-mail]>
Acked-by: Song Liu <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>

include/uapi/linux/bpf.h

···
 	};
 	__u8 tunnel_tos;
 	__u8 tunnel_ttl;
-	__u16 tunnel_ext;
+	__u16 tunnel_ext;	/* Padding, future use. */
 	__u32 tunnel_label;
 };
 
···
 	__u32 reqid;
 	__u32 spi;	/* Stored in network byte order */
 	__u16 family;
+	__u16 ext;	/* Padding, future use. */
 	union {
 		__u32 remote_ipv4;	/* Stored in network byte order */
 		__u32 remote_ipv6[4];	/* Stored in network byte order */

net/core/filter.c

···
 	to->tunnel_id = be64_to_cpu(info->key.tun_id);
 	to->tunnel_tos = info->key.tos;
 	to->tunnel_ttl = info->key.ttl;
+	to->tunnel_ext = 0;
 
 	if (flags & BPF_F_TUNINFO_IPV6) {
 		memcpy(to->remote_ipv6, &info->key.u.ipv6.src,
···
 		to->tunnel_label = be32_to_cpu(info->key.label);
 	} else {
 		to->remote_ipv4 = be32_to_cpu(info->key.u.ipv4.src);
+		memset(&to->remote_ipv6[1], 0, sizeof(__u32) * 3);
+		to->tunnel_label = 0;
 	}
 
 	if (unlikely(size != sizeof(struct bpf_tunnel_key)))
···
 	to->reqid = x->props.reqid;
 	to->spi = x->id.spi;
 	to->family = x->props.family;
+	to->ext = 0;
+
 	if (to->family == AF_INET6) {
 		memcpy(to->remote_ipv6, x->props.saddr.a6,
 		       sizeof(to->remote_ipv6));
 	} else {
 		to->remote_ipv4 = x->props.saddr.a4;
+		memset(&to->remote_ipv6[1], 0, sizeof(__u32) * 3);
 	}
 
 	return 0;