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Date: Mon, 21 Jul 2008 21:59:57 +0200 (CEST)
From: Roman Zippel <zippel@...ux-m68k.org>
To: Michael Kerrisk <mtk.manpages@...glemail.com>
cc: john stultz <johnstul@...ibm.com>,
lkml <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: ADJ_OFFSET_SS_READ bug?
Hi,
On Mon, 21 Jul 2008, Michael Kerrisk wrote:
> >> Sort of a quick off the cuff patch, but does the following look like the
> >> right fix to you?
I would more prefer a patch like below, instead of adding tests for this
all over the place this separates the code more clearly, as this syscall
is seriously overloaded.
bye, Roman
[PATCH] fix ADJ_OFFSET_SS_READ bug and do_adjtimex cleanup
Thanks to the review by Michael Kerrisk <mtk.manpages@...glemail.com> a
bug in the recent ADJ_OFFSET_SS_READ option was discovered, where the
ntp time_offset was inadvertently set by it. This fixes this by making
the adjtime code more separate from the ntp_adjtime code (both of which
really want to be separate syscalls).
Signed-off-by: Roman Zippel <zippel@...ux-m68k.org>
---
include/linux/timex.h | 9 +++++
kernel/time/ntp.c | 76 ++++++++++++++++++++++++++------------------------
2 files changed, 48 insertions(+), 37 deletions(-)
Index: linux-2.6/include/linux/timex.h
===================================================================
--- linux-2.6.orig/include/linux/timex.h
+++ linux-2.6/include/linux/timex.h
@@ -141,8 +141,15 @@ struct timex {
#define ADJ_MICRO 0x1000 /* select microsecond resolution */
#define ADJ_NANO 0x2000 /* select nanosecond resolution */
#define ADJ_TICK 0x4000 /* tick value */
+
+#ifdef __KERNEL__
+#define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */
+#define ADJ_OFFSET_SINGLESHOT 0x0001 /* old-fashioned adjtime */
+#define ADJ_OFFSET_READONLY 0x2000 /* read-only adjtime */
+#else
#define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */
-#define ADJ_OFFSET_SS_READ 0xa001 /* read-only adjtime */
+#define ADJ_OFFSET_SS_READ 0xa001 /* read-only adjtime */
+#endif
/* xntp 3.4 compatibility names */
#define MOD_OFFSET ADJ_OFFSET
Index: linux-2.6/kernel/time/ntp.c
===================================================================
--- linux-2.6.orig/kernel/time/ntp.c
+++ linux-2.6/kernel/time/ntp.c
@@ -277,38 +277,50 @@ static inline void notify_cmos_timer(voi
int do_adjtimex(struct timex *txc)
{
struct timespec ts;
- long save_adjust, sec;
int result;
- /* In order to modify anything, you gotta be super-user! */
- if (txc->modes && !capable(CAP_SYS_TIME))
- return -EPERM;
-
- /* Now we validate the data before disabling interrupts */
-
- if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) {
+ /* Validate the data before disabling interrupts */
+ if (txc->modes & ADJ_ADJTIME) {
/* singleshot must not be used with any other mode bits */
- if (txc->modes & ~ADJ_OFFSET_SS_READ)
+ if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
return -EINVAL;
- }
+ if (!(txc->modes & ADJ_OFFSET_READONLY) &&
+ !capable(CAP_SYS_TIME))
+ return -EPERM;
+ } else {
+ /* In order to modify anything, you gotta be super-user! */
+ if (txc->modes && !capable(CAP_SYS_TIME))
+ return -EPERM;
+
+ /* if the quartz is off by more than 10% something is VERY wrong! */
+ if (txc->modes & ADJ_TICK &&
+ (txc->tick < 900000/USER_HZ ||
+ txc->tick > 1100000/USER_HZ))
+ return -EINVAL;
- /* if the quartz is off by more than 10% something is VERY wrong ! */
- if (txc->modes & ADJ_TICK)
- if (txc->tick < 900000/USER_HZ ||
- txc->tick > 1100000/USER_HZ)
- return -EINVAL;
+ if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
+ hrtimer_cancel(&leap_timer);
+ }
- if (time_state != TIME_OK && txc->modes & ADJ_STATUS)
- hrtimer_cancel(&leap_timer);
getnstimeofday(&ts);
write_seqlock_irq(&xtime_lock);
- /* Save for later - semantics of adjtime is to return old value */
- save_adjust = time_adjust;
-
/* If there are input parameters, then process them */
+ if (txc->modes & ADJ_ADJTIME) {
+ long save_adjust = time_adjust;
+
+ if (!(txc->modes & ADJ_OFFSET_READONLY)) {
+ /* adjtime() is independent from ntp_adjtime() */
+ time_adjust = txc->offset;
+ ntp_update_frequency();
+ }
+ txc->offset = save_adjust;
+ goto adj_done;
+ }
if (txc->modes) {
+ long sec;
+
if (txc->modes & ADJ_STATUS) {
if ((time_status & STA_PLL) &&
!(txc->status & STA_PLL)) {
@@ -375,13 +387,8 @@ int do_adjtimex(struct timex *txc)
if (txc->modes & ADJ_TAI && txc->constant > 0)
time_tai = txc->constant;
- if (txc->modes & ADJ_OFFSET) {
- if (txc->modes == ADJ_OFFSET_SINGLESHOT)
- /* adjtime() is independent from ntp_adjtime() */
- time_adjust = txc->offset;
- else
- ntp_update_offset(txc->offset);
- }
+ if (txc->modes & ADJ_OFFSET)
+ ntp_update_offset(txc->offset);
if (txc->modes & ADJ_TICK)
tick_usec = txc->tick;
@@ -389,19 +396,16 @@ int do_adjtimex(struct timex *txc)
ntp_update_frequency();
}
+ txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
+ NTP_SCALE_SHIFT);
+ if (!(time_status & STA_NANO))
+ txc->offset /= NSEC_PER_USEC;
+
+adj_done:
result = time_state; /* mostly `TIME_OK' */
if (time_status & (STA_UNSYNC|STA_CLOCKERR))
result = TIME_ERROR;
- if ((txc->modes == ADJ_OFFSET_SINGLESHOT) ||
- (txc->modes == ADJ_OFFSET_SS_READ))
- txc->offset = save_adjust;
- else {
- txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
- NTP_SCALE_SHIFT);
- if (!(time_status & STA_NANO))
- txc->offset /= NSEC_PER_USEC;
- }
txc->freq = shift_right((s32)(time_freq >> PPM_SCALE_INV_SHIFT) *
(s64)PPM_SCALE_INV,
NTP_SCALE_SHIFT);
--
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