Date: Thu, 22 Jul 2010 19:36:22 +0200 (CEST)
From: Jan Engelhardt <jengelh@medozas.de>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Jeremy Allison <jra@samba.org>, Volker.Lendecke@sernet.de,
        David Howells <dhowells@redhat.com>, linux-cifs@vger.kernel.org,
        linux-nfs@vger.kernel.org, samba-technical@lists.samba.org,
        linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk,
        linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 02/18] xstat: Add a pair of system calls to make extended
 file stats available [ver #6]
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On Thursday 2010-07-22 19:16, Trond Myklebust wrote:
>> >But the fact is, th Unix ctime semantics are insane and largely
>> >useless. There's a damn good reason almost nobody uses ctime under
>> >unix.
>> 
>> I beg to differ. ctime is not completely useless. It reflects changes on 
>> the inode for when you don't you change the content. It's like an mtime 
>> for the metadata. It comes useful when you go around in your filesystem 
>> trying to figure out who of your co-admins screwed up the permissions on 
>> /etc/passwd... and if the mtime is the same as that of the last backup, 
>> I can at least have a reasonable assurance that it was /only/ the 
>> metadata that was tampered with. (SHA1 check, yeah yeah, costly on large 
>> files.)
>
>Errr... Only if you eliminate utimes() from your syscall table.
>Otherwise it is trivial to reset the mtime after changing the file
>contents.

Well yes; I had implicitly implied that evil people with malicious intent
are absent.