From: Kees Cook <[email protected]> Hey Thomas, Wanted to see if maybe there was still time for this for 3.8? thanks -john
The pstore RAM backend can get called during resume, and must be defensive against a suspended time source. Expose getnstimeofday logic that returns an error instead of a WARN. This can be detected and the timestamp can be zeroed out. Reported-by: Doug Anderson <[email protected]> Cc: Anton Vorontsov <[email protected]> Cc: Thomas Gleixner <[email protected]> Signed-off-by: Kees Cook <[email protected]> Signed-off-by: John Stultz <[email protected]> --- fs/pstore/ram.c | 10 +++++++--- include/linux/time.h | 1 + kernel/time/timekeeping.c | 29 ++++++++++++++++++++++++----- 3 files changed, 32 insertions(+), 8 deletions(-) diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c index 1a4f6da..dacfe78 100644 --- a/fs/pstore/ram.c +++ b/fs/pstore/ram.c @@ -168,12 +168,16 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type, static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz) { char *hdr; - struct timeval timestamp; + struct timespec timestamp; size_t len; - do_gettimeofday(×tamp); + /* Report zeroed timestamp if called before timekeeping has resumed. */ + if (__getnstimeofday(×tamp)) { + timestamp.tv_sec = 0; + timestamp.tv_nsec = 0; + } hdr = kasprintf(GFP_ATOMIC, RAMOOPS_KERNMSG_HDR "%lu.%lu\n", - (long)timestamp.tv_sec, (long)timestamp.tv_usec); + (long)timestamp.tv_sec, (long)(timestamp.tv_nsec / 1000)); WARN_ON_ONCE(!hdr); len = hdr ? strlen(hdr) : 0; persistent_ram_write(prz, hdr, len); diff --git a/include/linux/time.h b/include/linux/time.h index 4d358e9..0015aea 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -158,6 +158,7 @@ extern int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue); extern unsigned int alarm_setitimer(unsigned int seconds); extern int do_getitimer(int which, struct itimerval *value); +extern int __getnstimeofday(struct timespec *tv); extern void getnstimeofday(struct timespec *tv); extern void getrawmonotonic(struct timespec *ts); extern void getnstime_raw_and_real(struct timespec *ts_raw, diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 4c7de02..dfc7f87 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -214,19 +214,18 @@ static void timekeeping_forward_now(struct timekeeper *tk) } /** - * getnstimeofday - Returns the time of day in a timespec + * __getnstimeofday - Returns the time of day in a timespec. * @ts: pointer to the timespec to be set * - * Returns the time of day in a timespec. + * Updates the time of day in the timespec. + * Returns 0 on success, or -ve when suspended (timespec will be undefined). */ -void getnstimeofday(struct timespec *ts) +int __getnstimeofday(struct timespec *ts) { struct timekeeper *tk = &timekeeper; unsigned long seq; s64 nsecs = 0; - WARN_ON(timekeeping_suspended); - do { seq = read_seqbegin(&tk->lock); @@ -237,6 +236,26 @@ void getnstimeofday(struct timespec *ts) ts->tv_nsec = 0; timespec_add_ns(ts, nsecs); + + /* + * Do not bail out early, in case there were callers still using + * the value, even in the face of the WARN_ON. + */ + if (unlikely(timekeeping_suspended)) + return -EAGAIN; + return 0; +} +EXPORT_SYMBOL(__getnstimeofday); + +/** + * getnstimeofday - Returns the time of day in a timespec. + * @ts: pointer to the timespec to be set + * + * Returns the time of day in a timespec (WARN if suspended). + */ +void getnstimeofday(struct timespec *ts) +{ + WARN_ON(__getnstimeofday(ts)); } EXPORT_SYMBOL(getnstimeofday); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
