linux-kernel - Re: [PATCH v4 2/6] mounts: keep list of mounts in an rbtree

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Message-ID: <e9ceb034-e37e-f0af-aee1-85f573a41418@themaw.net>
Date:   Tue, 31 Oct 2023 09:23:34 +0800
From:   Ian Kent <raven@...maw.net>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-man@...r.kernel.org,
        linux-security-module@...r.kernel.org, Karel Zak <kzak@...hat.com>,
        David Howells <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian@...uner.io>,
        Amir Goldstein <amir73il@...il.com>,
        Matthew House <mattlloydhouse@...il.com>,
        Florian Weimer <fweimer@...hat.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v4 2/6] mounts: keep list of mounts in an rbtree

On 30/10/23 17:06, Miklos Szeredi wrote:
> On Mon, Oct 30, 2023 at 6:45 AM Ian Kent <raven@...maw.net> wrote:
>
>> Is fs/namespace.c:iterate_mounts() a problem?
>>
>> It's called from:
>>
>> 1) ./kernel/audit_tree.c:709: if (iterate_mounts(compare_root,
>> 2) ./kernel/audit_tree.c:839:    err = iterate_mounts(tag_mount, tree, mnt);
>> 3) ./kernel/audit_tree.c:917:        failed = iterate_mounts(tag_mount,
>> tree, tagged);
>>
>>
>>   From functions 1) audit_trim_trees(), 2) audit_add_tree_rule() and
>>
>> 3) audit_tag_tree().
> So that interface works like this:
>
>   - collect_mounts() creates a temporary copy of a mount tree, mounts
> are chained on mnt_list.

Right, sorry for the noise, I didn't look far enough.


Ian

>
>   - iterate_mounts() is used to do some work on the temporary tree
>
>   - drop_collected_mounts() frees the temporary tree
>
> These mounts are never installed in a namespace.  My guess is that a
> private copy is used instead of the original mount tree to prevent
> races.
>
> Thanks,
> Miklos
>