time: Improve sanity checking of timekeeping inputs

commit 4e8b14526ca7fb046a81c94002c1c43b6fdf0e9b upstream

Unexpected behavior could occur if the time is set to a value large
enough to overflow a 64bit ktime_t (which is something larger then the
year 2262).

Also unexpected behavior could occur if large negative offsets are
injected via adjtimex.

So this patch improves the sanity check timekeeping inputs by
improving the timespec_valid() check, and then makes better use of
timespec_valid() to make sure we don't set the time to an invalid
negative value or one that overflows ktime_t.

Note: This does not protect from setting the time close to overflowing
ktime_t and then letting natural accumulation cause the overflow.

Reported-by: CAI Qian <caiqian@redhat.com>
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Zhouping Liu <zliu@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/1344454580-17031-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/ktime.h b/include/linux/ktime.h
index 603bec2913b00ca40086149828f3fcddab32a435..06177ba10a1617461dbe6803efc22ba6dfb43304 100644 (file)
--- a/include/linux/ktime.h
+++ b/include/linux/ktime.h
@@ -58,13 +58,6 @@ union ktime {
 
 typedef union ktime ktime_t;           /* Kill this */
 
-#define KTIME_MAX                      ((s64)~((u64)1 << 63))
-#if (BITS_PER_LONG == 64)
-# define KTIME_SEC_MAX                 (KTIME_MAX / NSEC_PER_SEC)
-#else
-# define KTIME_SEC_MAX                 LONG_MAX
-#endif
-
 /*
  * ktime_t definitions when using the 64-bit scalar representation:
  */

diff --git a/include/linux/time.h b/include/linux/time.h
index b3061782dec3851765f3c398f67179744f4a39c2..c8f723374a7013a6b8178364b7571adb5de3ffbf 100644 (file)
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -107,11 +107,29 @@ static inline struct timespec timespec_sub(struct timespec lhs,
        return ts_delta;
 }
 
+#define KTIME_MAX                      ((s64)~((u64)1 << 63))
+#if (BITS_PER_LONG == 64)
+# define KTIME_SEC_MAX                 (KTIME_MAX / NSEC_PER_SEC)
+#else
+# define KTIME_SEC_MAX                 LONG_MAX
+#endif
+
 /*
  * Returns true if the timespec is norm, false if denorm:
  */
-#define timespec_valid(ts) \
-       (((ts)->tv_sec >= 0) && (((unsigned long) (ts)->tv_nsec) < NSEC_PER_SEC))
+static inline bool timespec_valid(const struct timespec *ts)
+{
+       /* Dates before 1970 are bogus */
+       if (ts->tv_sec < 0)
+               return false;
+       /* Can't have more nanoseconds then a second */
+       if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
+               return false;
+       /* Disallow values that could overflow ktime_t */
+       if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
+               return false;
+       return true;
+}
 
 extern void read_persistent_clock(struct timespec *ts);
 extern void read_boot_clock(struct timespec *ts);

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 678ae3184efd24a024b32827644eb8d244eca01c..bfa6be73873c5d3e2983826de0c368e6bb231987 100644 (file)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -382,7 +382,7 @@ int do_settimeofday(const struct timespec *tv)
        struct timespec ts_delta;
        unsigned long flags;
 
-       if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
+       if (!timespec_valid(tv))
                return -EINVAL;
 
        write_seqlock_irqsave(&xtime_lock, flags);
@@ -417,6 +417,8 @@ EXPORT_SYMBOL(do_settimeofday);
 int timekeeping_inject_offset(struct timespec *ts)
 {
        unsigned long flags;
+       struct timespec tmp;
+       int ret = 0;
 
        if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
                return -EINVAL;
@@ -425,9 +427,16 @@ int timekeeping_inject_offset(struct timespec *ts)
 
        timekeeping_forward_now();
 
+       tmp = timespec_add(xtime,  *ts);
+       if (!timespec_valid(&tmp)) {
+               ret = -EINVAL;
+               goto error;
+       }
+
        xtime = timespec_add(xtime, *ts);
        wall_to_monotonic = timespec_sub(wall_to_monotonic, *ts);
 
+error: /* even if we error out, we forwarded the time, so call update */
        timekeeping_update(true);
 
        write_sequnlock_irqrestore(&xtime_lock, flags);
@@ -435,7 +444,7 @@ int timekeeping_inject_offset(struct timespec *ts)
        /* signal hrtimers about time change */
        clock_was_set();
 
-       return 0;
+       return ret;
 }
 EXPORT_SYMBOL(timekeeping_inject_offset);
 
@@ -582,7 +591,20 @@ void __init timekeeping_init(void)
        struct timespec now, boot;
 
        read_persistent_clock(&now);
+       if (!timespec_valid(&now)) {
+               pr_warn("WARNING: Persistent clock returned invalid value!\n"
+                       "         Check your CMOS/BIOS settings.\n");
+               now.tv_sec = 0;
+               now.tv_nsec = 0;
+       }
+
        read_boot_clock(&boot);
+       if (!timespec_valid(&boot)) {
+               pr_warn("WARNING: Boot clock returned invalid value!\n"
+                       "         Check your CMOS/BIOS settings.\n");
+               boot.tv_sec = 0;
+               boot.tv_nsec = 0;
+       }
 
        write_seqlock_irqsave(&xtime_lock, flags);