A time namespace fix and a matching selftest. The futex absolute timeouts

which are based on CLOCK_MONOTONIC require time namespace corrected. This
 was missed in the original time namesapce support.
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Merge tag 'timers-urgent-2020-10-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fixes from Thomas Gleixner:
 "A time namespace fix and a matching selftest. The futex absolute
  timeouts which are based on CLOCK_MONOTONIC require time namespace
  corrected. This was missed in the original time namesapce support"

* tag 'timers-urgent-2020-10-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  selftests/timens: Add a test for futex()
  futex: Adjust absolute futex timeouts with per time namespace offset

kernel/futex.c

@@ -39,6 +39,7 @@
 #include <linux/freezer.h>
 #include <linux/memblock.h>
 #include <linux/fault-inject.h>
+#include <linux/time_namespace.h>
 
 #include <asm/futex.h>
 
@@ -3797,6 +3798,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
 		t = timespec64_to_ktime(ts);
 		if (cmd == FUTEX_WAIT)
 			t = ktime_add_safe(ktime_get(), t);
+		else if (!(op & FUTEX_CLOCK_REALTIME))
+			t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
 		tp = &t;
 	}
 	/*
@@ -3989,6 +3992,8 @@ SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
 		t = timespec64_to_ktime(ts);
 		if (cmd == FUTEX_WAIT)
 			t = ktime_add_safe(ktime_get(), t);
+		else if (!(op & FUTEX_CLOCK_REALTIME))
+			t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
 		tp = &t;
 	}
 	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||

tools/testing/selftests/timens/Makefile

@@ -1,4 +1,4 @@
-TEST_GEN_PROGS := timens timerfd timer clock_nanosleep procfs exec
+TEST_GEN_PROGS := timens timerfd timer clock_nanosleep procfs exec futex
 TEST_GEN_PROGS_EXTENDED := gettime_perf
 
 CFLAGS := -Wall -Werror -pthread

tools/testing/selftests/timens/futex.c

@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <sched.h>
+
+#include <linux/unistd.h>
+#include <linux/futex.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "log.h"
+#include "timens.h"
+
+#define NSEC_PER_SEC 1000000000ULL
+
+static int run_test(int clockid)
+{
+	int futex_op = FUTEX_WAIT_BITSET;
+	struct timespec timeout, end;
+	int val = 0;
+
+	if (clockid == CLOCK_REALTIME)
+		futex_op |= FUTEX_CLOCK_REALTIME;
+
+	clock_gettime(clockid, &timeout);
+	timeout.tv_nsec += NSEC_PER_SEC / 10; // 100ms
+	if (timeout.tv_nsec > NSEC_PER_SEC) {
+		timeout.tv_sec++;
+		timeout.tv_nsec -= NSEC_PER_SEC;
+	}
+
+	if (syscall(__NR_futex, &val, futex_op, 0,
+		    &timeout, 0, FUTEX_BITSET_MATCH_ANY) >= 0) {
+		ksft_test_result_fail("futex didn't return ETIMEDOUT\n");
+		return 1;
+	}
+
+	if (errno != ETIMEDOUT) {
+		ksft_test_result_fail("futex didn't return ETIMEDOUT: %s\n",
+							strerror(errno));
+		return 1;
+	}
+
+	clock_gettime(clockid, &end);
+
+	if (end.tv_sec < timeout.tv_sec ||
+	    (end.tv_sec == timeout.tv_sec && end.tv_nsec < timeout.tv_nsec)) {
+		ksft_test_result_fail("futex slept less than 100ms\n");
+		return 1;
+	}
+
+
+	ksft_test_result_pass("futex with the %d clockid\n", clockid);
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	int status, len, fd;
+	char buf[4096];
+	pid_t pid;
+	struct timespec mtime_now;
+
+	nscheck();
+
+	ksft_set_plan(2);
+
+	clock_gettime(CLOCK_MONOTONIC, &mtime_now);
+
+	if (unshare_timens())
+		return 1;
+
+	len = snprintf(buf, sizeof(buf), "%d %d 0",
+			CLOCK_MONOTONIC, 70 * 24 * 3600);
+	fd = open("/proc/self/timens_offsets", O_WRONLY);
+	if (fd < 0)
+		return pr_perror("/proc/self/timens_offsets");
+
+	if (write(fd, buf, len) != len)
+		return pr_perror("/proc/self/timens_offsets");
+
+	close(fd);
+
+	pid = fork();
+	if (pid < 0)
+		return pr_perror("Unable to fork");
+	if (pid == 0) {
+		int ret = 0;
+
+		ret |= run_test(CLOCK_REALTIME);
+		ret |= run_test(CLOCK_MONOTONIC);
+		if (ret)
+			ksft_exit_fail();
+		ksft_exit_pass();
+		return 0;
+	}
+
+	if (waitpid(pid, &status, 0) != pid)
+		return pr_perror("Unable to wait the child process");
+
+	if (WIFEXITED(status))
+		return WEXITSTATUS(status);
+
+	return 1;
+}