From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jann Horn <jannh@google.com>,
Linux API <linux-api@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: new ...at() flag: AT_NO_JUMPS
Date: Thu, 4 May 2017 18:27:10 -0700 [thread overview]
Message-ID: <CA+55aFyOKM7DW7+0sdDFKdZFXgptb5r1id9=Wvhd8AgSP7qjwQ@mail.gmail.com> (raw)
In-Reply-To: <20170505003030.GM29622@ZenIV.linux.org.uk>
On Thu, May 4, 2017 at 5:30 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> As for mountpoint crossing... it might make sense to split those.
> O_BENEATH allowed it, and if we want AT_BENEATH to match that - let's
> do it. Then this one would become AT_BENEATH | AT_XDEV (the latter named
> after find(1) option, obviously).
So I would still like to split that NO_JUMP flag even more.
I like the AT_BENEATH | AT_XDEV split, but I think XDEV should be
split further, and I think the symlink avoidance should be split more
too.
As mentioned last time, at least for the git usage, even relative
symlinks are a no-no - not because they'd escape, but simply because
git wants to see the *unique* name, and resolve relative symlinks to
either the symlink, or to the actual file it points to.
So I think that we'd want an additional flag that says "no symlinks at all".
And I think the "no mountpoint" traversal might be splittable too.
Yes, sometimes you'd probably want to say "stay exactly inside this
filesystem" (like find -xdev). So no arguments against AT_XDEV that
refuses any mount traversal (kind of like my "no symlink traversal"
thing).
But at other points you might want to just guarantee that the walk
stays below a certain starting point and doesn't escape.
That could still allow crossing mount-points, but only if they are
non-bind mounts and cannot let us escape.
I'm not sure if that's testable, though.
Linus
next prev parent reply other threads:[~2017-05-05 1:27 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-29 22:04 new ...at() flag: AT_NO_JUMPS Al Viro
2017-04-29 23:17 ` Andy Lutomirski
2017-04-29 23:25 ` Al Viro
2017-04-30 1:13 ` Andy Lutomirski
2017-04-30 4:38 ` Matthew Wilcox
2017-04-30 16:10 ` Al Viro
2017-05-01 4:52 ` Andy Lutomirski
2017-05-01 5:15 ` Al Viro
2017-05-01 17:36 ` Jann Horn
2017-05-01 19:37 ` Andy Lutomirski
2017-05-05 0:30 ` Al Viro
2017-05-05 0:44 ` Andy Lutomirski
2017-05-05 1:06 ` Al Viro
2017-05-05 1:27 ` Linus Torvalds [this message]
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
2017-05-05 4:39 ` Al Viro
2017-05-05 4:44 ` Andy Lutomirski
2017-05-05 20:04 ` Eric W. Biederman
2017-05-05 20:28 ` Eric W. Biederman
2017-05-08 19:34 ` Mickaël Salaün
2017-05-18 8:50 ` David Drysdale
2017-09-10 20:26 Jürg Billeter
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