Re: [PATCH 2/3] y2038: linux: Provide __utimes64 implementation

[Lukasz Majewski <lukma@denx.de>]

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Hi Adhemerval,

> On 07/02/2020 10:00, Lukasz Majewski wrote:
> > This patch provides new __utimes64 explicit 64 bit function for
> > setting file's 64 bit attributes for access and modification time.
> > 
> > Internally, the __utimensat64_helper function is used. This patch
> > is necessary for having architectures with __WORDSIZE == 32 Y2038
> > safe.
> > 
> > Moreover, a 32 bit version - __utimes has been refactored to
> > internally use __utimes64.
> > 
> > The __utimes is now supposed to be used on systems still supporting
> > 32 bit time (__TIMESIZE != 64) - hence the necessary conversion of
> > struct timeval to 64 bit struct __timeval64.
> > 
> > Build tests:
> > ./src/scripts/build-many-glibcs.py glibcs
> > 
> > Run-time tests:
> > - Run specific tests on ARM/x86 32bit systems (qemu):
> >   https://github.com/lmajewski/meta-y2038 and run tests:
> >   https://github.com/lmajewski/y2038-tests/commits/master
> > 
> > Above tests were performed with Y2038 redirection applied as well
> > as without to test proper usage of both __utimes64 and __utimes.  
> 
> LGTM with some smalls changes below.
> 
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> 
> > ---
> >  include/time.h                   |  3 +++
> >  sysdeps/unix/sysv/linux/utimes.c | 37
> > ++++++++++++++++++++++---------- 2 files changed, 29 insertions(+),
> > 11 deletions(-)
> > 
> > diff --git a/include/time.h b/include/time.h
> > index e38f5e32e6..b04747889a 100644
> > --- a/include/time.h
> > +++ b/include/time.h
> > @@ -211,8 +211,11 @@ libc_hidden_proto (__clock_getres64);
> >  #endif
> >  
> >  #if __TIMESIZE == 64
> > +# define __utimes64 __utimes
> >  # define __utimensat64 __utimensat
> >  #else
> > +extern int __utimes64 (const char *file, const struct __timeval64
> > tvp[2]); +libc_hidden_proto (__utimes64)
> >  extern int __utimensat64 (int fd, const char *file,
> >                            const struct __timespec64 tsp[2], int
> > flags); libc_hidden_proto (__utimensat64);  
> 
> Ok.
> 
> > diff --git a/sysdeps/unix/sysv/linux/utimes.c
> > b/sysdeps/unix/sysv/linux/utimes.c index 121d883469..09c4e56f18
> > 100644 --- a/sysdeps/unix/sysv/linux/utimes.c
> > +++ b/sysdeps/unix/sysv/linux/utimes.c
> > @@ -16,22 +16,37 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >  
> > -#include <errno.h>
> > -#include <stddef.h>
> > -#include <utime.h>
> > -#include <sys/time.h>
> > -#include <sysdep.h>
> > +#include <time.h>
> >  
> > +int
> > +__utimes64 (const char *file, const struct __timeval64 tvp[2])
> > +{
> > +  struct __timespec64 ts64[2];
> > +
> > +  if (tvp)  
> 
> No implicit checks.

The documentation [1] and [2] explicitly says that times (here tvp) can
be NULL:
"If times is NULL, then the access and modification times of the file
are set to the current time. "

Hence, it is perfectly valid to pass the NULL to the
__utimensat64_helper(). Without this check we will segfault earlier
(before we reach proper syscall) and introduce regression in glibc.


Links:

[1] - https://linux.die.net/man/2/utimes
[2] - https://www.unix.com/man-page/linux/2/utimes/

> 
> > +    {
> > +      ts64[0] = timeval64_to_timespec64 (tvp[0]);
> > +      ts64[1] = timeval64_to_timespec64 (tvp[1]);
> > +    }
> > +
> > +  return __utimensat64_helper (0, file, tvp ? ts64 : NULL, 0);
> > +}  
> 
> Ok.
> 
> >  
> > -/* Consider moving to syscalls.list.  */
> > +#if __TIMESIZE != 64
> > +libc_hidden_def (__utimes64)
> >  
> > -/* Change the access time of FILE to TVP[0] and
> > -   the modification time of FILE to TVP[1].  */
> >  int
> >  __utimes (const char *file, const struct timeval tvp[2])
> >  {
> > -  /* Avoid implicit array coercion in syscall macros.  */
> > -  return INLINE_SYSCALL (utimes, 2, file, &tvp[0]);
> > -}
> > +  struct __timeval64 tv64[2];
> >  
> > +  if (tvp)  
> 
> No implicit checks.

Please consider the above comment.

> 
> > +    {
> > +      tv64[0] = valid_timeval_to_timeval64 (tvp[0]);
> > +      tv64[1] = valid_timeval_to_timeval64 (tvp[1]);
> > +    }
> > +
> > +  return __utimes64 (file, tvp ? tv64 : NULL);
> > +}
> > +#endif
> >  weak_alias (__utimes, utimes)
> >   
> 
> Ok.




Best regards,

Lukasz Majewski

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