From: Jamie Lokier <jamie-yetKDKU6eevNLxjTenLetw@public.gmane.org>
To: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Cc: Michael Kerrisk
<mtk.manpages-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>,
Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA@public.gmane.org>,
drepper-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] utimensat() non-conformances and fixes [v3]
Date: Tue, 3 Jun 2008 13:10:15 +0100 [thread overview]
Message-ID: <20080603121015.GC28905@shareable.org> (raw)
In-Reply-To: <20080603120850.GZ28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Al Viro wrote:
> On Tue, Jun 03, 2008 at 01:01:35PM +0100, Jamie Lokier wrote:
> > > with a lot of things, starting with "why utimes(2) has weaker requirements
> > > with NULL argument", but we are far too late to fix that.
> >
> > To be fair, having a writable file descriptor only lets you change the
> > mtime to "now", and having a readable file descriptor only lets you
> > change the atime to "now".
> >
> > Changing the times _in general_ can be seen as over-reaching those
> > capabilities and arguably justifies more strict checks.
>
> Which is what all questions about writability apply only to NULL case
> anyway...
Oh!
So if I have the file descriptor, I can just as well change the mtime
by read a byte and write it back. Or even do a zero-length write, on
some OSes.
-- Jamie
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WARNING: multiple messages have this Message-ID (diff)
From: Jamie Lokier <jamie@shareable.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>,
Miklos Szeredi <miklos@szeredi.hu>,
drepper@redhat.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, linux-man@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] utimensat() non-conformances and fixes [v3]
Date: Tue, 3 Jun 2008 13:10:15 +0100 [thread overview]
Message-ID: <20080603121015.GC28905@shareable.org> (raw)
In-Reply-To: <20080603120850.GZ28946@ZenIV.linux.org.uk>
Al Viro wrote:
> On Tue, Jun 03, 2008 at 01:01:35PM +0100, Jamie Lokier wrote:
> > > with a lot of things, starting with "why utimes(2) has weaker requirements
> > > with NULL argument", but we are far too late to fix that.
> >
> > To be fair, having a writable file descriptor only lets you change the
> > mtime to "now", and having a readable file descriptor only lets you
> > change the atime to "now".
> >
> > Changing the times _in general_ can be seen as over-reaching those
> > capabilities and arguably justifies more strict checks.
>
> Which is what all questions about writability apply only to NULL case
> anyway...
Oh!
So if I have the file descriptor, I can just as well change the mtime
by read a byte and write it back. Or even do a zero-length write, on
some OSes.
-- Jamie
next prev parent reply other threads:[~2008-06-03 12:10 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-16 8:31 [PATCH] utimensat() non-conformances and fixes -- version 2 Michael Kerrisk
2008-05-16 8:31 ` Michael Kerrisk
[not found] ` <482D4665.4050401-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2008-05-16 8:34 ` Michael Kerrisk
2008-05-16 8:34 ` Michael Kerrisk
2008-05-16 16:59 ` Miklos Szeredi
2008-05-16 16:59 ` Miklos Szeredi
[not found] ` <E1Jx3Gw-0002eA-55-8f8m9JG5TPIdUIPVzhDTVZP2KDSNp7ea@public.gmane.org>
2008-05-17 19:57 ` Michael Kerrisk
2008-05-17 19:57 ` Michael Kerrisk
2008-05-19 9:50 ` Miklos Szeredi
2008-05-19 9:50 ` Miklos Szeredi
2008-05-19 10:12 ` Miklos Szeredi
2008-05-19 12:24 ` Michael Kerrisk
2008-05-19 13:17 ` Miklos Szeredi
2008-05-30 15:34 ` [PATCH] utimensat() non-conformances and fixes [v3] Michael Kerrisk
2008-05-30 15:34 ` Michael Kerrisk
[not found] ` <48401E7E.9090304-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2008-05-30 16:37 ` Miklos Szeredi
2008-05-30 16:37 ` Miklos Szeredi
2008-05-30 18:24 ` Michael Kerrisk
2008-05-30 19:22 ` Miklos Szeredi
[not found] ` <E1K2ABK-0002ck-UT-8f8m9JG5TPIdUIPVzhDTVZP2KDSNp7ea@public.gmane.org>
2008-05-30 19:32 ` Matthew Wilcox
2008-05-30 19:32 ` Matthew Wilcox
[not found] ` <20080530193207.GB28074-6jwH94ZQLHl74goWV3ctuw@public.gmane.org>
2008-05-30 20:08 ` Miklos Szeredi
2008-05-30 20:08 ` Miklos Szeredi
[not found] ` <cfd18e0f0805301124o5f217dden10726b268d05d81a-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-05-30 19:43 ` Michael Kerrisk
2008-05-30 19:43 ` Michael Kerrisk
[not found] ` <cfd18e0f0805301243h7d862963o8320a2c1f48942ce-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-05-30 20:17 ` Miklos Szeredi
2008-05-30 20:17 ` Miklos Szeredi
[not found] ` <E1K2B2k-0002kS-Cz-8f8m9JG5TPIdUIPVzhDTVZP2KDSNp7ea@public.gmane.org>
2008-05-31 5:28 ` Michael Kerrisk
2008-05-31 5:28 ` Michael Kerrisk
2008-05-30 20:17 ` Andrew Morton
2008-05-31 5:44 ` Michael Kerrisk
2008-06-03 11:05 ` Michael Kerrisk
[not found] ` <cfd18e0f0806030405u1c32b114pa0fdd979f36f87fb-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-06-03 11:13 ` Miklos Szeredi
2008-06-03 11:13 ` Miklos Szeredi
2008-06-03 11:22 ` Al Viro
2008-06-03 11:27 ` Michael Kerrisk
2008-06-03 11:30 ` Jamie Lokier
[not found] ` <20080603113018.GA27955-yetKDKU6eevNLxjTenLetw@public.gmane.org>
2008-06-03 11:39 ` Michael Kerrisk
2008-06-03 11:39 ` Michael Kerrisk
2008-06-03 11:49 ` Al Viro
[not found] ` <20080603114921.GX28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-06-03 11:58 ` Al Viro
2008-06-03 11:58 ` Al Viro
2008-06-03 12:01 ` Jamie Lokier
[not found] ` <20080603120135.GA28905-yetKDKU6eevNLxjTenLetw@public.gmane.org>
2008-06-03 12:08 ` Al Viro
2008-06-03 12:08 ` Al Viro
[not found] ` <20080603120850.GZ28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-06-03 12:10 ` Jamie Lokier [this message]
2008-06-03 12:10 ` Jamie Lokier
[not found] ` <20080603112221.GW28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-06-03 12:16 ` Miklos Szeredi
2008-06-03 12:16 ` Miklos Szeredi
2008-06-03 13:05 ` Al Viro
2008-06-03 11:52 ` Michael Kerrisk
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