unix: a unix name can be a non-null terminated string

In this patch, we replace all zero characters to '@'.

==30==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60300000e3ca at pc 0x7f34144b6be1 bp 0x7ffee7b6bb20 sp 0x7ffee7b6b298
READ of size 26 at 0x60300000e3ca thread T0
    #0 0x7f34144b6be0  (/lib64/libasan.so.3+0x8dbe0)
    #1 0x7f34144b8e4d in __interceptor_vsnprintf (/lib64/libasan.so.3+0x8fe4d)
    #2 0x4966cb in vprint_on_level criu/log.c:228
    #3 0x496b64 in print_on_level criu/log.c:249
    #4 0x505c94 in collect_one_unixsk criu/sk-unix.c:1401
    #5 0x4e7ae3 in collect_image criu/protobuf.c:213
    #6 0x462c5c in root_prepare_shared criu/cr-restore.c:247
    #7 0x462c5c in restore_task_with_children criu/cr-restore.c:1420
    #8 0x7f34132d70ec in __clone (/lib64/libc.so.6+0x1030ec)

0x60300000e3ca is located 0 bytes to the right of 26-byte region [0x60300000e3b0,0x60300000e3ca)
allocated by thread T0 here:
    #0 0x7f34144efe70 in malloc (/lib64/libasan.so.3+0xc6e70)
    #1 0x7f3413bdb021  (/lib64/libprotobuf-c.so.1+0x6021)
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/sk-unix.c

@@ -975,6 +975,9 @@ static int bind_unix_sk(int sk, struct unix_sk_info *ui)
 	int cwd_fd = -1, root_fd = -1;
 	int ret = -1;
 
+	if (ui->ue->name.len == 0)
+		return 0;
+
 	if ((ui->ue->type == SOCK_STREAM) && (ui->ue->state == TCP_ESTABLISHED)) {
 		/*
 		 * FIXME this can be done, but for doing this properly we
@@ -1362,6 +1365,8 @@ static int collect_one_unixsk(void *o, ProtobufCMessage *base, struct cr_img *i)
 {
 	struct unix_sk_info *ui = o;
 	static bool post_queued = false;
+	char *uname, *prefix = "";
+	int ulen;
 
 	ui->ue = pb_msg(base, UnixSkEntry);
 	ui->name_dir = (void *)ui->ue->name_dir;
@@ -1391,10 +1396,32 @@ static int collect_one_unixsk(void *o, ProtobufCMessage *base, struct cr_img *i)
 	INIT_LIST_HEAD(&ui->connected);
 	INIT_LIST_HEAD(&ui->node);
 	ui->flags = 0;
-	pr_info(" `- Got %#x peer %#x (name %s dir %s)\n",
+
+	uname = ui->name;
+	ulen = ui->ue->name.len;
+	if (ulen > 0 && uname[0] == 0) {
+		prefix = "@";
+		uname++;
+		ulen--;
+		if (memrchr(uname, 0, ulen)) {
+			/* replace zero characters */
+			char *s = alloca(ulen + 1);
+			int i;
+
+			for (i = 0; i < ulen; i++)
+				s[i] = uname[i] ? : '@';
+			uname = s;
+		}
+	} else if (ulen == 0) {
+		ulen = 1;
+		uname = "-";
+	}
+
+	pr_info(" `- Got %#x peer %#x (name %s%.*s dir %s)\n",
 		ui->ue->ino, ui->ue->peer,
-		ui->name ? (ui->name[0] ? ui->name : &ui->name[1]) : "-",
+		prefix, ulen, uname,
 		ui->name_dir ? ui->name_dir : "-");
+
 	list_add_tail(&ui->list, &unix_sockets);
 	return file_desc_add(&ui->d, ui->ue->id, &unix_desc_ops);
 }