From: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
To: Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Jann Horn <jannh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Linux Kernel Mailing List
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
linux-fsdevel
<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
David Drysdale <drysdale-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Subject: Re: new ...at() flag: AT_NO_JUMPS
Date: Fri, 5 May 2017 05:39:02 +0100 [thread overview]
Message-ID: <20170505043902.GP29622@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFy1SokNNUgxBnFLdA1PRyeG13BqyYNg5xVrW-tNGqh2Bg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Thu, May 04, 2017 at 08:46:49PM -0700, Linus Torvalds wrote:
> On Thu, May 4, 2017 at 7:47 PM, Jann Horn <jannh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> wrote:
> >
> > Thread 1 starts an AT_BENEATH path walk using an O_PATH fd
> > pointing to /srv/www/example.org/foo; the path given to the syscall is
> > "bar/../../../../etc/passwd". The path walk enters the "bar" directory.
> > Thread 2 moves /srv/www/example.org/foo/bar to
> > /srv/www/example.org/bar.
> > Thread 1 processes the rest of the path ("../../../../etc/passwd"), never
> > hitting /srv/www/example.org/foo in the process.
> >
> > I'm not really familiar with the VFS internals, but from a coarse look
> > at the patch, it seems like it wouldn't block this?
>
> I think you're right.
>
> I guess it would be safe for the RCU case due to the sequence number
> check, but not the non-RCU case.
Yes and no... FWIW, to exclude that it would suffice to have
mount --rbind /src/www/example.org/foo /srv/www/example.org/foo done first.
Then this kind of race will end up with -ENOENT due to path_connected()
logics in follow_dotdot_rcu()/follow_dotdot(). I'm not sure about the
intended applications, though - is that thing supposed to be used along with
some horror like seccomp, or...?
next prev parent reply other threads:[~2017-05-05 4:39 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-29 22:04 new ...at() flag: AT_NO_JUMPS Al Viro
[not found] ` <20170429220414.GT29622-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2017-04-29 23:17 ` Andy Lutomirski
[not found] ` <CALCETrXhOhG0tRDDOROwT9ghvQvKziM2PBN=CX5Soa2m7=0cFw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-29 23:25 ` Al Viro
2017-04-30 1:13 ` Andy Lutomirski
[not found] ` <20170429232504.GU29622-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2017-04-30 4:38 ` Matthew Wilcox
[not found] ` <20170430043822.GE27790-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
2017-04-30 16:10 ` Al Viro
2017-05-01 4:52 ` Andy Lutomirski
[not found] ` <CALCETrX0dx3d6OQQ+1GJ_xgSz3iNVeRn+8o6b-+3f7awVOWdQg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-01 5:15 ` Al Viro
2017-05-01 17:36 ` Jann Horn
2017-05-01 19:37 ` Andy Lutomirski
[not found] ` <CAG48ez0wccvQ5i+XN_Q_yA9_ZwSaGb-W+zky0KQb_GU=9G+MSw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-05 0:30 ` Al Viro
2017-05-05 0:44 ` Andy Lutomirski
2017-05-05 1:06 ` Al Viro
[not found] ` <20170505003030.GM29622-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2017-05-05 1:27 ` Linus Torvalds
[not found] ` <CA+55aFyOKM7DW7+0sdDFKdZFXgptb5r1id9=Wvhd8AgSP7qjwQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-05 3:00 ` Al Viro
2017-05-05 4:01 ` Linus Torvalds
2017-05-05 4:31 ` Andy Lutomirski
2017-05-05 2:47 ` Jann Horn
2017-05-05 3:46 ` Linus Torvalds
[not found] ` <CA+55aFy1SokNNUgxBnFLdA1PRyeG13BqyYNg5xVrW-tNGqh2Bg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-05 4:39 ` Al Viro [this message]
2017-05-05 4:44 ` Andy Lutomirski
[not found] ` <CALCETrVQ2fwDZOsGSoLyRb6Qjp4nszfDjOPSYi0kzqt23Aw1NA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-05 20:04 ` Eric W. Biederman
2017-05-05 20:28 ` Eric W. Biederman
[not found] ` <8737cj6oao.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-05-08 19:34 ` Mickaël Salaün
2017-05-18 8:50 ` David Drysdale
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