linux-kernel - Re: [PATCH 2/3] exec: Make unlocking exec_update

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Date:   Tue, 07 Apr 2020 11:21:57 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Bernd Edlinger <bernd.edlinger@...mail.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexey Gladkov <gladkov.alexey@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH 2/3] exec: Make unlocking exec_update_mutex explict

Christian Brauner <christian.brauner@...ntu.com> writes:

> On Mon, Apr 06, 2020 at 08:31:52PM -0500, Eric W. Biederman wrote:
>> 
>> With install_exec_creds updated to follow immediately after
>> setup_new_exec, the failure of unshare_sighand is the only
>> code path where exec_update_mutex is held but not explicitly
>> unlocked.
>> 
>> Update that code path to explicitly unlock exec_update_mutex.
>> 
>> Remove the unlocking of exec_update_mutex from free_bprm.
>> 
>> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
>
> Yeah, assuming that I didn't miss any subtleties just now.
> By "explicit" I assume you mean not conditionally unlocked, i.e. we
> don't need to check any condition in free_binprm().

Yes.  Not conditionally unlocked is what I meant.

> Acked-by: Christian Brauner <christian.brauner@...ntu.com>

Eric