linux-kernel - [PATCH v2 3/4] fs/proc: apply timens offset for start

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Message-Id: <20201008053944.32718-4-michael.weiss@aisec.fraunhofer.de>
Date:   Thu,  8 Oct 2020 07:39:43 +0200
From:   Michael Weiß <michael.weiss@...ec.fraunhofer.de>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Andrei Vagin <avagin@...il.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Christian Brauner <christian.brauner@...ntu.com>
Cc:     linux-kernel@...r.kernel.org,
        Michael Weiß <michael.weiss@...ec.fraunhofer.de>
Subject: [PATCH v2 3/4] fs/proc: apply timens offset for start_boottime of processes

Since start_boottime of processes are seconds since boottime and the
boottime stamp is now shifted according to the timens offset, the
offset of the time namespace also needs to be applied before the
process stats are given to userspace.

This avoids that processes shown, e.g., by 'ps' appear as time
travelers in the corresponding time namespace.

Signed-off-by: Michael Weiß <michael.weiss@...ec.fraunhofer.de>
---
 fs/proc/array.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 65ec2029fa80..277f654f289e 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -56,6 +56,7 @@
 #include <linux/types.h>
 #include <linux/errno.h>
 #include <linux/time.h>
+#include <linux/time_namespace.h>
 #include <linux/kernel.h>
 #include <linux/kernel_stat.h>
 #include <linux/tty.h>
@@ -533,8 +534,9 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	priority = task_prio(task);
 	nice = task_nice(task);
 
-	/* convert nsec -> ticks */
-	start_time = nsec_to_clock_t(task->start_boottime);
+	/* apply timens offset for boottime and convert nsec -> ticks */
+	start_time =
+		nsec_to_clock_t(timens_add_boottime_ns(task->start_boottime));
 
 	seq_put_decimal_ull(m, "", pid_nr_ns(pid, ns));
 	seq_puts(m, " (");
-- 
2.20.1