Commit 42e729b9 authored Jan 21, 2018 by Deepa Dinamani

utimes: Clamp the timestamps before update

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>
Acked-by: Jeff Layton <jlayton@kernel.org>

parent f8b92ba6

fs/utimes.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -36,16 +36,14 @@ 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 = timestamp_truncate(times[0], inode);
		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 = timestamp_truncate(times[1], inode);
		newattrs.ia_valid \|= ATTR_MTIME_SET;
		}
		/*

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