From 94d440d618467806009c8edc70b094d64e12ee5a Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@gmail.com>
Date: Sat, 11 Apr 2020 08:40:31 -0700
Subject: [PATCH] proc, time/namespace: Show clock symbolic names in /proc/pid/timens_offsets
Git-commit: 94d440d618467806009c8edc70b094d64e12ee5a
Patch-mainline: v5.7-rc2
References: bsc#1164648,jsc#SLE-11493

Michael Kerrisk suggested to replace numeric clock IDs with symbolic names.

Now the content of these files looks like this:
$ cat /proc/774/timens_offsets
monotonic      864000         0
boottime      1728000         0

For setting offsets, both representations of clocks (numeric and symbolic)
can be used.

As for compatibility, it is acceptable to change things as long as
userspace doesn't care. The format of timens_offsets files is very new and
there are no userspace tools yet which rely on this format.

But three projects crun, util-linux and criu rely on the interface of
setting time offsets and this is why it's required to continue supporting
the numeric clock IDs on write.

Fixes: 04a8682a71be ("fs/proc: Introduce /proc/pid/timens_offsets")
Suggested-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200411154031.642557-1-avagin@gmail.com
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

---
 fs/proc/base.c          | 14 +++++++++++++-
 kernel/time/namespace.c | 15 ++++++++++++++-
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 6042b646ab27..572898dd16a0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1573,6 +1573,7 @@ static ssize_t timens_offsets_write(struct file *file, const char __user *buf,
 	noffsets = 0;
 	for (pos = kbuf; pos; pos = next_line) {
 		struct proc_timens_offset *off = &offsets[noffsets];
+		char clock[10];
 		int err;
 
 		/* Find the end of line and ensure we don't look past it */
@@ -1584,10 +1585,21 @@ static ssize_t timens_offsets_write(struct file *file, const char __user *buf,
 				next_line = NULL;
 		}
 
-		err = sscanf(pos, "%u %lld %lu", &off->clockid,
+		err = sscanf(pos, "%9s %lld %lu", clock,
 				&off->val.tv_sec, &off->val.tv_nsec);
 		if (err != 3 || off->val.tv_nsec >= NSEC_PER_SEC)
 			goto out;
+
+		clock[sizeof(clock) - 1] = 0;
+		if (strcmp(clock, "monotonic") == 0 ||
+		    strcmp(clock, __stringify(CLOCK_MONOTONIC)) == 0)
+			off->clockid = CLOCK_MONOTONIC;
+		else if (strcmp(clock, "boottime") == 0 ||
+			 strcmp(clock, __stringify(CLOCK_BOOTTIME)) == 0)
+			off->clockid = CLOCK_BOOTTIME;
+		else
+			goto out;
+
 		noffsets++;
 		if (noffsets == ARRAY_SIZE(offsets)) {
 			if (next_line)
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index 3b30288793fe..53bce347cd50 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -338,7 +338,20 @@ static struct user_namespace *timens_owner(struct ns_common *ns)
 
 static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts)
 {
-	seq_printf(m, "%d %lld %ld\n", clockid, ts->tv_sec, ts->tv_nsec);
+	char *clock;
+
+	switch (clockid) {
+	case CLOCK_BOOTTIME:
+		clock = "boottime";
+		break;
+	case CLOCK_MONOTONIC:
+		clock = "monotonic";
+		break;
+	default:
+		clock = "unknown";
+		break;
+	}
+	seq_printf(m, "%-10s %10lld %9ld\n", clock, ts->tv_sec, ts->tv_nsec);
 }
 
 void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m)
-- 
2.16.4