linux-kernel - [PATCH 3/5] selftests/seccomp: Add test for wait killable notifier

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Message-Id: <20210318051733.2544-4-sargun@sargun.me>
Date:   Wed, 17 Mar 2021 22:17:31 -0700
From:   Sargun Dhillon <sargun@...gun.me>
To:     Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>
Cc:     Sargun Dhillon <sargun@...gun.me>,
        Mauricio Vásquez Bernal <mauricio@...volk.io>,
        Rodrigo Campos <rodrigo@...volk.io>,
        Tycho Andersen <tycho@...ho.pizza>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: [PATCH 3/5] selftests/seccomp: Add test for wait killable notifier

This adds a test for the positive case of the wait killable notifier,
in testing that when the feature is activated the process acts as
expected -- in not terminating on a non-fatal signal, and instead
queueing it up. There is already a test case for normal handlers
and preemption.

Signed-off-by: Sargun Dhillon <sargun@...gun.me>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 64 +++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 26c72f2b61b1..48ad53030d5a 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -235,6 +235,10 @@ struct seccomp_notif_addfd {
 };
 #endif
 
+#ifndef SECCOMP_USER_NOTIF_FLAG_WAIT_KILLABLE
+#define SECCOMP_USER_NOTIF_FLAG_WAIT_KILLABLE	(1UL << 0) /* Prevent task from being interrupted */
+#endif
+
 struct seccomp_notif_addfd_small {
 	__u64 id;
 	char weird[4];
@@ -4139,6 +4143,66 @@ TEST(user_notification_addfd_rlimit)
 	close(memfd);
 }
 
+TEST(user_notification_signal_wait_killable)
+{
+	pid_t pid;
+	long ret;
+	int status, listener, sk_pair[2];
+	struct seccomp_notif req = {
+		.flags = SECCOMP_USER_NOTIF_FLAG_WAIT_KILLABLE,
+	};
+	struct seccomp_notif_resp resp = {};
+	char c;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	ASSERT_EQ(socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair), 0);
+	ASSERT_EQ(fcntl(sk_pair[0], F_SETFL, O_NONBLOCK), 0);
+
+	listener = user_notif_syscall(__NR_gettid,
+				      SECCOMP_FILTER_FLAG_NEW_LISTENER);
+	ASSERT_GE(listener, 0);
+
+	pid = fork();
+	ASSERT_GE(pid, 0);
+
+	if (pid == 0) {
+		close(sk_pair[0]);
+		handled = sk_pair[1];
+		if (signal(SIGUSR1, signal_handler) == SIG_ERR) {
+			perror("signal");
+			exit(1);
+		}
+
+		ret = syscall(__NR_gettid);
+		exit(!(ret == 42));
+	}
+	close(sk_pair[1]);
+
+	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+	EXPECT_EQ(kill(pid, SIGUSR1), 0);
+	/* Make sure we didn't get a signal */
+	EXPECT_EQ(read(sk_pair[0], &c, 1), -1);
+	/* Make sure the notification is still alive */
+	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_ID_VALID, &req.id), 0);
+
+	resp.id = req.id;
+	resp.error = 0;
+	resp.val = 42;
+
+	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
+
+	EXPECT_EQ(waitpid(pid, &status, 0), pid);
+	EXPECT_EQ(true, WIFEXITED(status));
+	EXPECT_EQ(0, WEXITSTATUS(status));
+	/* Check we eventually received the signal */
+	EXPECT_EQ(read(sk_pair[0], &c, 1), 1);
+}
+
+
 /*
  * TODO:
  * - expand NNP testing
-- 
2.25.1