> On Feb 15, 2016, at 11:01, Deepa Dinamani <[email protected]> wrote: > > long/ kernel_time_t is 32 bit on a 32 bit system and > 64 bit on a 64 bit system. > > ceph_encode_timespec() encodes only the lower 32 bits on > a 64 bit system and encodes all of 32 bits on a 32bit > system. > > ceph_decode_timespec() decodes 32 bit tv_sec and tv_nsec > into kernel_time_t/ long. > > The encode and decode functions do not match when the > values are negative: > > Consider the following scenario on a 32 bit system: > When a negative number is cast to u32 as encode does, the > value is positive and is greater than INT_MAX. Decode reads > back this value. And, this value cannot be represented by > long on 32 bit systems. So by section 6.3.1.3 of the > C99 standard, the result is implementation defined. > > Consider the following scenario on a 64 bit system: > When a negative number is cast to u32 as encode does, the > value is positive. This value is later assigned by decode > function by a cast to long. Since this value can be > represented in long data type, this becomes a positive > value greater than INT_MAX. But, the value encoded was > negative, so the encode and decode functions do not match. > > Change the decode function as follows to overcome the above > bug: > The decode should first cast the value to a s64 this will > be positive value greater than INT_MAX(in case of a negative > encoded value)and then cast this value again as s32, which > drops the higher order 32 bits. > On 32 bit systems, this is the right value in kernel_time_t/ > long. > On 64 bit systems, assignment to kernel_time_t/ long > will sign extend this value to reflect the signed bit encoded. > > Assume ceph timestamp ranges permitted are 1902..2038. > > Suggested-by: Arnd Bergmann <[email protected]> > Signed-off-by: Deepa Dinamani <[email protected]> > --- > include/linux/ceph/decode.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/ceph/decode.h b/include/linux/ceph/decode.h > index a6ef9cc..e777e99 100644 > --- a/include/linux/ceph/decode.h > +++ b/include/linux/ceph/decode.h > @@ -137,8 +137,8 @@ bad: > static inline void ceph_decode_timespec(struct timespec *ts, > const struct ceph_timespec *tv) > { > - ts->tv_sec = (__kernel_time_t)le32_to_cpu(tv->tv_sec); > - ts->tv_nsec = (long)le32_to_cpu(tv->tv_nsec); > + ts->tv_sec = (s32)(s64)le32_to_cpu(tv->tv_sec); > + ts->tv_nsec = (s32)(s64)le32_to_cpu(tv->tv_nsec); > } > static inline void ceph_encode_timespec(struct ceph_timespec *tv, > const struct timespec *ts)
Applied, thanks Yan, Zheng > -- > 1.9.1 > _______________________________________________ Y2038 mailing list [email protected] https://lists.linaro.org/mailman/listinfo/y2038
