From: Andrei Vagin avagin@gmail.com
commit 94d440d618467806009c8edc70b094d64e12ee5a upstream.
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: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/proc/base.c | 14 +++++++++++++- kernel/time/namespace.c | 15 ++++++++++++++- 2 files changed, 27 insertions(+), 2 deletions(-)
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1573,6 +1573,7 @@ static ssize_t timens_offsets_write(stru 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(stru 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) --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -337,7 +337,20 @@ static struct user_namespace *timens_own
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)