sock_diag: fix filter code sent to userspace

Filters need to be translated to real BPF code for userland, like SO_GETFILTER.
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/filter.h

@@ -46,6 +46,7 @@ extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
 extern int sk_detach_filter(struct sock *sk);
 extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen);
 extern int sk_get_filter(struct sock *sk, struct sock_filter __user *filter, unsigned len);
+extern void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to);
 
 #ifdef CONFIG_BPF_JIT
 #include <stdarg.h>

net/core/filter.c

@@ -778,7 +778,7 @@ int sk_detach_filter(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(sk_detach_filter);
 
-static void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to)
+void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to)
 {
 	static const u16 decodes[] = {
 		[BPF_S_ALU_ADD_K]	= BPF_ALU|BPF_ADD|BPF_K,

net/core/sock_diag.c

@@ -73,8 +73,13 @@ int sock_diag_put_filterinfo(struct user_namespace *user_ns, struct sock *sk,
 		goto out;
 	}
 
-	if (filter)
-		memcpy(nla_data(attr), filter->insns, len);
+	if (filter) {
+		struct sock_filter *fb = (struct sock_filter *)nla_data(attr);
+		int i;
+
+		for (i = 0; i < filter->len; i++, fb++)
+			sk_decode_filter(&filter->insns[i], fb);
+	}
 
 out:
 	rcu_read_unlock();