lkml.org 
[lkml]   [2019]   [Aug]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [Y2038] [PATCH 05/20] utimes: Clamp the timestamps before update
    On Mon, Aug 5, 2019 at 6:30 AM Ben Hutchings
    <ben.hutchings@codethink.co.uk> wrote:
    >
    > On Mon, 2019-07-29 at 18:49 -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)
    >
    > This is testing the un-clamped value.
    >
    > > + 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)
    >
    > Similarly here, for the minimum.
    >
    > I suggest testing for clamping like this:
    >
    > if (newattrs.ia_atime.tv_sec != times[0].tv_sec)
    > ...
    > if (newattrs.ia_mtime.tv_sec != times[1].tv_sec)
    > ...
    >
    > Ben.
    >
    > > + newattrs.ia_mtime.tv_nsec = 0;
    > > + else
    > > + newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
    > > newattrs.ia_valid |= ATTR_MTIME_SET;
    > > }

    Darrick pointed out that maybe we could use timestamp_truncate() here to clamp.
    I think it is ok to truncate to the right granularity also here.
    setattr callbacks do it already. So the diff here looks like below:

    - 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_atime = timestamp_truncate(times[0], inode);

    Thanks,
    Deepa

    \
     
     \ /
      Last update: 2019-08-10 22:38    [W:4.103 / U:0.236 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site