zdtm: add scm07 SCM_RIGHTS & SCM_CREDENTIALS case

Reproducer for the next problem:

When unix socket contains SCM with SCM_CREDENTIALS
cmsg_type we have to postpone saving this packet to
CR_FD_SK_QUEUES image because we need to have information
about process which creds was transfered in this message.
But if this SkPacketEntry already contains data from
SCM_RIGHTS messages (file descriptors was transfered
through unix socket) we will lose this data because of
incorrect queue_packet_entry function implementation.

This problem tends to inconsistent CRIU dump and on
restore we will get:

Error (criu/files.c:230): Empty list on file desc id 13(5)
Error (criu/files.c:232): BUG at criu/files.c:232

Reviewed-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>

(cherry picked from commit 6aa13217721db06b7cbd873e615580f0a455d5a7)
Signed-off-by: Ahmed Elaidy <elaidya225@gmail.com>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

test/zdtm/static/Makefile

@@ -231,6 +231,7 @@ TST_NOFILE	:=				\
 		scm04				\
 		scm05				\
 		scm06				\
+		scm07				\
 		scm09				\
 		aio00				\
 		aio01				\

test/zdtm/static/scm07.c

@@ -0,0 +1,203 @@
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc = "Check that SCM_RIGHTS & SCM_CREDENTIALS are preserved";
+const char *test_author = "Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>";
+
+static int send_fd(int via, int fd)
+{
+	struct msghdr h = {};
+	struct cmsghdr *ch;
+	struct iovec iov = {
+		.iov_base = (char *)"FDSTORE=1",
+		.iov_len = sizeof("FDSTORE=1"),
+	};
+	char buf[CMSG_SPACE(sizeof(int))];
+	int *fdp;
+
+	h.msg_control = buf;
+	h.msg_controllen = sizeof(buf);
+	ch = CMSG_FIRSTHDR(&h);
+	ch->cmsg_level = SOL_SOCKET;
+	ch->cmsg_type = SCM_RIGHTS;
+	ch->cmsg_len = CMSG_LEN(sizeof(int));
+	fdp = (int *)CMSG_DATA(ch);
+	*fdp = fd;
+	h.msg_iov = &iov;
+	h.msg_iovlen = 1;
+
+	if (sendmsg(via, &h, 0) <= 0)
+		return -1;
+
+	return 0;
+}
+
+static int send_creds(int via)
+{
+	struct msghdr h = {};
+	struct cmsghdr *ch;
+	struct iovec iov = {
+		.iov_base = (char *)"CREDS=1",
+		.iov_len = sizeof("CREDS=1"),
+	};
+	char buf[CMSG_SPACE(sizeof(struct ucred))];
+	struct ucred *ucred;
+
+	h.msg_control = buf;
+	h.msg_controllen = sizeof(buf);
+	ch = CMSG_FIRSTHDR(&h);
+	ch->cmsg_level = SOL_SOCKET;
+	ch->cmsg_type = SCM_CREDENTIALS;
+	ch->cmsg_len = CMSG_LEN(sizeof(struct ucred));
+	ucred = (struct ucred *)CMSG_DATA(ch);
+	ucred->pid = getpid();
+	ucred->uid = getuid();
+	ucred->gid = getgid();
+	h.msg_iov = &iov;
+	h.msg_iovlen = 1;
+
+	if (sendmsg(via, &h, 0) <= 0)
+		return -1;
+
+	return 0;
+}
+
+static int recv_fd(int via)
+{
+	struct msghdr h = {};
+	struct cmsghdr *ch;
+	char iovbuf[128];
+	struct iovec iov = {
+		.iov_base = iovbuf,
+		.iov_len = sizeof(iovbuf),
+	};
+	char buf[1024];
+	int *fdp = NULL;
+
+next_msg:
+	h.msg_control = buf;
+	h.msg_controllen = sizeof(buf);
+	h.msg_iov = &iov;
+	h.msg_iovlen = 1;
+
+	if (recvmsg(via, &h, MSG_DONTWAIT) <= 0) {
+		if (errno == EAGAIN || errno == EWOULDBLOCK)
+			return -3;
+		else
+			return -1;
+	}
+
+	if (h.msg_flags & MSG_TRUNC)
+		return -2;
+
+	for (ch = CMSG_FIRSTHDR(&h); ch; ch = CMSG_NXTHDR(&h, ch)) {
+		if (ch->cmsg_type != SCM_RIGHTS)
+			continue;
+
+		fdp = (int *)CMSG_DATA(ch);
+	}
+
+	if (!fdp)
+		goto next_msg;
+
+	return fdp ? *fdp : -4;
+}
+
+int main(int argc, char **argv)
+{
+	int sk[2] = { -1, -1 }, p[2] = { -1, -1 }, rfd, ret = 1;
+
+#define MSG "HELLO"
+	char buf[8]; /* bigger than the MSG to check boundaries */
+
+	test_init(argc, argv);
+
+	if (socketpair(PF_UNIX, SOCK_DGRAM, 0, sk) < 0) {
+		pr_perror("Can't make unix pair");
+		exit(1);
+	}
+
+	if (setsockopt(sk[0], SOL_SOCKET, SO_PASSCRED, &(int){ 1 }, sizeof(int)) < 0 ||
+	    setsockopt(sk[1], SOL_SOCKET, SO_PASSCRED, &(int){ 1 }, sizeof(int)) < 0) {
+		pr_perror("setsockopt SO_PASSCRED");
+		close(sk[0]);
+		close(sk[1]);
+		exit(1);
+	}
+
+	if (send_creds(sk[0]) < 0) {
+		pr_perror("Can't send creds");
+		close(sk[0]);
+		close(sk[1]);
+		exit(1);
+	}
+
+	/*
+	 * We want to send this socket through
+	 * "sk" unix socket.
+	 *
+	 * Also, we will send ucreds through "sk"
+	 * unix socket.
+	 */
+	if (socketpair(PF_UNIX, SOCK_STREAM, 0, p) < 0) {
+		pr_perror("Can't make socketpair to send");
+		close(sk[0]);
+		close(sk[1]);
+		exit(1);
+	}
+
+	if (send_fd(sk[0], p[1]) < 0) {
+		pr_perror("Can't send descriptor");
+		close(sk[0]);
+		close(sk[1]);
+		close(p[0]);
+		close(p[1]);
+		exit(1);
+	}
+
+	/* we sent this side of socketpair */
+	close(p[1]);
+
+	test_daemon();
+	test_waitsig();
+
+	rfd = recv_fd(sk[1]);
+	if (rfd < 0) {
+		fail("Can't recv sk back (%d)", rfd);
+		goto out;
+	}
+
+	if (write(p[0], MSG, sizeof(MSG)) != sizeof(MSG)) {
+		fail("Socket write-broken");
+		goto out;
+	}
+
+	if (read(rfd, buf, sizeof(buf)) != sizeof(MSG)) {
+		fail("Socket read-broken");
+		goto out;
+	}
+
+	if (strcmp(buf, MSG)) {
+		buf[sizeof(buf) - 1] = '\0';
+		fail("Socket read-broken (%s)", buf);
+		goto out;
+	}
+
+	pass();
+	ret = 0;
+out:
+	if (p[0] > 0)
+		close(p[0]);
+	if (rfd > 0)
+		close(rfd);
+	if (sk[0] > 0)
+		close(sk[0]);
+	if (sk[1] > 0)
+		close(sk[1]);
+	return ret;
+}

test/zdtm/static/scm07.desc

@@ -0,0 +1 @@
+{'flags': 'suid'}