Re: [Y2038] [PATCH 05/20] utimes: Clamp the timestamps before update

On Wed, Jul 31, 2019 at 8:15 AM Darrick J. Wong darrick.wong@oracle.com wrote:

On Mon, Jul 29, 2019 at 06:49:09PM -0700, Deepa Dinamani wrote:

...

POSIX is ambiguous on the behavior of timestamps for futimens, utimensat and utimes. Whether to return an error or silently clamp a timestamp beyond the range supported by the underlying filesystems is not clear.

POSIX.1 section for futimens, utimensat and utimes says: (http://pubs.opengroup.org/onlinepubs/9699919799/functions/futimens.html)

The file's relevant timestamp shall be set to the greatest value supported by the file system that is not greater than the specified time.

If the tv_nsec field of a timespec structure has the special value UTIME_NOW, the file's relevant timestamp shall be set to the greatest value supported by the file system that is not greater than the current time.

[EINVAL] A new file timestamp would be a value whose tv_sec component is not a value supported by the file system.

The patch chooses to clamp the timestamps according to the filesystem timestamp ranges and does not return an error. This is in line with the behavior of utime syscall also since the POSIX page(http://pubs.opengroup.org/onlinepubs/009695399/functions/utime.html) for utime does not mention returning an error or clamping like above.

Same for utimes http://pubs.opengroup.org/onlinepubs/009695399/functions/utimes.html

Signed-off-by: Deepa Dinamani deepa.kernel@gmail.com

fs/utimes.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/fs/utimes.c b/fs/utimes.c index 350c9c16ace1..4c1a2ce90bbc 100644 --- a/fs/utimes.c +++ b/fs/utimes.c @@ -21,6 +21,7 @@ static int utimes_common(const struct path *path, struct timespec64 *times) int error; struct iattr newattrs; struct inode *inode = path->dentry->d_inode;

• struct super_block *sb = inode->i_sb;
  struct inode *delegated_inode = NULL;
  
  error = mnt_want_write(path->mnt);
  

@@ -36,16 +37,24 @@ static int utimes_common(const struct path *path, struct timespec64 *times) if (times[0].tv_nsec == UTIME_OMIT) newattrs.ia_valid &= ~ATTR_ATIME; else if (times[0].tv_nsec != UTIME_NOW) {

•                 newattrs.ia_atime.tv_sec = times[0].tv_sec;
  

•                 newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
  

•                 newattrs.ia_atime.tv_sec =
  

•                         clamp(times[0].tv_sec, sb->s_time_min, sb->s_time_max);
  

•                 if (times[0].tv_sec == sb->s_time_max || times[0].tv_sec == sb->s_time_min)
  

•                         newattrs.ia_atime.tv_nsec = 0;
  

•                 else
  

•                         newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
                  newattrs.ia_valid |= ATTR_ATIME_SET;
          }
  
          if (times[1].tv_nsec == UTIME_OMIT)
                  newattrs.ia_valid &= ~ATTR_MTIME;
          else if (times[1].tv_nsec != UTIME_NOW) {
  

•                 newattrs.ia_mtime.tv_sec = times[1].tv_sec;
  

•                 newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
  

•                 newattrs.ia_mtime.tv_sec =
  

•                         clamp(times[1].tv_sec, sb->s_time_min, sb->s_time_max);
  

•                 if (times[1].tv_sec >= sb->s_time_max || times[1].tv_sec == sb->s_time_min)
  

Line length.

Also, didn't you just introduce a function to clamp tv_sec and fix granularity? Why not just use it here? I think this is the third time I've seen this open-coded logic.

Yes, we can use that now. Earlier we were not setting the tv_nsec to 0 in timestamp_truncate() which is why this was opencoded here. I will make the change to include this.

Thanks, Deepa