[PATCH 5/5] selftests/seccomp: Add test for atomic addfd+send

From: Sargun Dhillon <sargun@sargun.me>
To: Kees Cook <keescook@chromium.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux Containers <containers@lists.linux-foundation.org>
Cc: "Sargun Dhillon" <sargun@sargun.me>,
	"Mauricio Vásquez Bernal" <mauricio@kinvolk.io>,
	"Rodrigo Campos" <rodrigo@kinvolk.io>,
	"Tycho Andersen" <tycho@tycho.pizza>,
	"Giuseppe Scrivano" <gscrivan@redhat.com>,
	"Christian Brauner" <christian.brauner@ubuntu.com>
Subject: [PATCH 5/5] selftests/seccomp: Add test for atomic addfd+send
Date: Wed, 17 Mar 2021 22:17:33 -0700	[thread overview]
Message-ID: <20210318051733.2544-6-sargun@sargun.me> (raw)
In-Reply-To: <20210318051733.2544-1-sargun@sargun.me>

This just adds a test to verify that when using the new introduced flag
to ADDFD, a valid fd is added and returned as the syscall result.

Signed-off-by: Rodrigo Campos <rodrigo@kinvolk.io>
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 48ad53030d5a..f7242294a2d5 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -239,6 +239,10 @@ struct seccomp_notif_addfd {
 #define SECCOMP_USER_NOTIF_FLAG_WAIT_KILLABLE	(1UL << 0) /* Prevent task from being interrupted */
 #endif
 
+#ifndef SECCOMP_ADDFD_FLAG_SEND
+#define SECCOMP_ADDFD_FLAG_SEND	(1UL << 1) /* Addfd and return it, atomically */
+#endif
+
 struct seccomp_notif_addfd_small {
 	__u64 id;
 	char weird[4];
@@ -3980,8 +3984,14 @@ TEST(user_notification_addfd)
 	ASSERT_GE(pid, 0);
 
 	if (pid == 0) {
+		/* fds will be added and this value is expected */
 		if (syscall(__NR_getppid) != USER_NOTIF_MAGIC)
 			exit(1);
+
+		/* Atomic addfd+send is received here. Check it is a valid fd */
+		if (fcntl(syscall(__NR_getppid), F_GETFD) == -1)
+			exit(1);
+
 		exit(syscall(__NR_getppid) != USER_NOTIF_MAGIC);
 	}
 
@@ -4064,6 +4074,30 @@ TEST(user_notification_addfd)
 	ASSERT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
 	ASSERT_EQ(addfd.id, req.id);
 
+	/* Verify we can do an atomic addfd and send */
+	addfd.newfd = 0;
+	addfd.flags = SECCOMP_ADDFD_FLAG_SEND;
+	fd = ioctl(listener, SECCOMP_IOCTL_NOTIF_ADDFD, &addfd);
+
+	/* Child has fds 0-6 and 42 used, we expect the lower fd available: 7 */
+	EXPECT_EQ(fd, 7);
+	EXPECT_EQ(filecmp(getpid(), pid, memfd, fd), 0);
+
+	/*
+	 * This sets the ID of the ADD FD to the last request plus 1. The
+	 * notification ID increments 1 per notification.
+	 */
+	addfd.id = req.id + 1;
+
+	/* This spins until the underlying notification is generated */
+	while (ioctl(listener, SECCOMP_IOCTL_NOTIF_ADDFD, &addfd) != -1 &&
+	       errno != -EINPROGRESS)
+		nanosleep(&delay, NULL);
+
+	memset(&req, 0, sizeof(req));
+	ASSERT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+	ASSERT_EQ(addfd.id, req.id);
+
 	resp.id = req.id;
 	resp.error = 0;
 	resp.val = USER_NOTIF_MAGIC;
@@ -4124,6 +4158,10 @@ TEST(user_notification_addfd_rlimit)
 	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_ADDFD, &addfd), -1);
 	EXPECT_EQ(errno, EMFILE);
 
+	addfd.flags = SECCOMP_ADDFD_FLAG_SEND;
+	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_ADDFD, &addfd), -1);
+	EXPECT_EQ(errno, EMFILE);
+
 	addfd.newfd = 100;
 	addfd.flags = SECCOMP_ADDFD_FLAG_SETFD;
 	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_ADDFD, &addfd), -1);
-- 
2.25.1

