On Wed, Jun 4, 2008 at 6:37 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>> The POSIX.1 draft spec for utimensat() says that to do anything
>> other than setting both timestamps to a time other than the
>> current time (i.e., times is not NULL, and both tv_nsec fields
>> are not UTIME_NOW and both tv_nsec fields are not UTIME_OMIT),
>> either:
>>
>> a) the caller's effective user ID must match the file owner; or
>> b) the caller must have appropriate privileges.
>>
>> If this condition is violated, then the error EPERM should result.
>> However, the current implementation does not generate EPERM if
>> one tv_nsec field is UTIME_NOW while the other is UTIME_OMIT.
>> It should give this error for that case.
>>
>> This patch:
>>
>> a) Repairs that problem.
>> b) Removes the now unneeded nsec_special() helper function.
>>
>> Miklos suggested an alternative idea, migrating the
>> is_owner_or_cap() checks into fs/attr.c:inode_change_ok() via
>> the use of an ATTR_OWNER_CHECK flag. Maybe we could do that
>> later, but for now I've gone with this version, which is
>> simpler, and can be more easily read as being correct.
>
> Wise decision.
>
>> CC: Miklos Szeredi <miklos@xxxxxxxxxx>
>> CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
>> CC: Ulrich Drepper <drepper@xxxxxxxxxx>
>> Signed-off-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
>>
>>
>> --- linux-2.6.26-rc4/fs/utimes.c 2008-06-03 23:11:53.000000000 +0200
>> +++ linux-2.6.26-rc4-utimensat-fix-v4/fs/utimes.c 2008-06-03 23:04:48.000000000 +0200
>> @@ -40,14 +40,9 @@
>>
>> #endif
>>
>> -static bool nsec_special(long nsec)
>> -{
>> - return nsec == UTIME_OMIT || nsec == UTIME_NOW;
>> -}
>> -
>> static bool nsec_valid(long nsec)
>> {
>> - if (nsec_special(nsec))
>> + if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
>> return true;
>>
>> return nsec >= 0 && nsec <= 999999999;
>> @@ -135,8 +130,7 @@
>> * UTIME_NOW, then need to check permissions, because
>> * inode_change_ok() won't do it.
>> */
>> - if (!times || (nsec_special(times[0].tv_nsec) &&
>> - nsec_special(times[1].tv_nsec))) {
>> + if (!times) {
>
> This can be restored to be the "else" branch of the "if (times)".
Yes. Thanks.
>> error = -EACCES;
>> if (IS_IMMUTABLE(inode))
>> goto mnt_drop_write_and_out;
>> @@ -151,6 +145,18 @@
>> goto mnt_drop_write_and_out;
>> }
>> }
>> + } else if ((times[0].tv_nsec == UTIME_NOW &&
>> + times[1].tv_nsec == UTIME_OMIT)
>> + ||
>> + (times[0].tv_nsec == UTIME_OMIT &&
>> + times[1].tv_nsec == UTIME_NOW)) {
>
> And I'd rather put this inside the "if (times)" for clarity.
Yes.
>
>> + error =-EPERM;
>> +
>> + if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
>> + goto mnt_drop_write_and_out;
>
> And then you would've realized, that this check was already done.
Quite!
I'll make these changes and test.
Cheers,
Michael
>> +
>> + if (!is_owner_or_cap(inode))
>> + goto mnt_drop_write_and_out;
>
> OK.
>
>> }
>> mutex_lock(&inode->i_mutex);
>> error = notify_change(dentry, &newattrs);
>>
>>
>>
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html
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