From: Matthew Wilcox <willy@infradead.org>
To: Ross Zwisler <zwisler@chromium.org>
Cc: linux-kernel@vger.kernel.org,
Mattias Nissler <mnissler@chromium.org>,
Benjamin Gordon <bmgordon@google.com>,
Ross Zwisler <zwisler@google.com>,
Raul Rangel <rrangel@google.com>,
Micah Morton <mortonm@google.com>,
Dmitry Torokhov <dtor@google.com>, Jan Kara <jack@suse.cz>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v4] Add a "nosymfollow" mount option.
Date: Thu, 30 Jan 2020 16:45:58 -0800 [thread overview]
Message-ID: <20200131004558.GA6699@bombadil.infradead.org> (raw)
In-Reply-To: <20200131002750.257358-1-zwisler@google.com>
On Thu, Jan 30, 2020 at 05:27:50PM -0700, Ross Zwisler wrote:
> For mounts that have the new "nosymfollow" option, don't follow
> symlinks when resolving paths. The new option is similar in spirit to
> the existing "nodev", "noexec", and "nosuid" options. Various BSD
> variants have been supporting the "nosymfollow" mount option for a
> long time with equivalent implementations.
>
> Note that symlinks may still be created on file systems mounted with
> the "nosymfollow" option present. readlink() remains functional, so
> user space code that is aware of symlinks can still choose to follow
> them explicitly.
>
> Setting the "nosymfollow" mount option helps prevent privileged
> writers from modifying files unintentionally in case there is an
> unexpected link along the accessed path. The "nosymfollow" option is
> thus useful as a defensive measure for systems that need to deal with
> untrusted file systems in privileged contexts.
The openat2 series was just merged yesterday which includes a
LOOKUP_NO_SYMLINKS option. Is this enough for your needs, or do you
need the mount option?
https://lore.kernel.org/linux-fsdevel/20200129142709.GX23230@ZenIV.linux.org.uk/
next prev parent reply other threads:[~2020-01-31 0:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 0:27 Ross Zwisler
2020-01-31 0:45 ` Matthew Wilcox [this message]
2020-01-31 1:51 ` Aleksa Sarai
2020-01-31 21:20 ` Ross Zwisler
2020-02-01 6:27 ` Aleksa Sarai
2020-02-03 22:15 ` Ross Zwisler
2020-02-09 9:12 ` Aleksa Sarai
2020-01-31 19:55 ` Ross Zwisler
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