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From: Andy Lutomirski <luto@kernel.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>
Subject: Re: new ...at() flag: AT_NO_JUMPS
Date: Sat, 29 Apr 2017 18:13:27 -0700	[thread overview]
Message-ID: <CALCETrVue8VyJDUSgy9Hsw67mxddirwDr703OBM_fWm9Hzvb4A@mail.gmail.com> (raw)
In-Reply-To: <20170429232504.GU29622@ZenIV.linux.org.uk>

On Sat, Apr 29, 2017 at 4:25 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Sat, Apr 29, 2017 at 04:17:18PM -0700, Andy Lutomirski wrote:
>> On Sat, Apr 29, 2017 at 3:04 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>> > New AT_... flag - AT_NO_JUMPS
>> >
>> > Semantics: pathname resolution must not involve
>> >         * traversals of absolute symlinks
>> >         * traversals of procfs-style symlinks
>> >         * traversals of mountpoints (including bindings, referrals, etc.)
>> >         * traversal of .. in the starting point of pathname resolution.
>>
>> Can you clarify this last one?  I assume that ".." will be rejected,
>> but what about "a/../.."?  How about "b" if b is a symlink to ".."?
>> How about "a/b" if a is a directory and b is a symlink to "../.."?
>
> All of those will be rejected - in each of those cases pathname traversal
> leads back into the starting point with .. being the next component to
> handle.

Sounds good.

Might it make sense to split it into two flags, one to prevent moving
between mounts and one for everything else?  I can imagine webservers
and such that are fine with traversing mount points but don't want to
escape their home directory.

--Andy

  reply	other threads:[~2017-04-30  1:14 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-29 22:04 Al Viro
2017-04-29 23:17 ` Andy Lutomirski
2017-04-29 23:25   ` Al Viro
2017-04-30  1:13     ` Andy Lutomirski [this message]
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
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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