linux-kernel - Re: [PATCH] fs: exec: apply CLOEXEC before changing dumpable task flags

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Message-ID: <20161220172955.GA7776@redhat.com>
Date:   Tue, 20 Dec 2016 18:29:56 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Aleksa Sarai <asarai@...e.de>
Cc:     viro@...iv.linux.org.uk, ebiederm@...ssion.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        cyphar@...har.com, dev@...ncontainers.org
Subject: Re: [PATCH] fs: exec: apply CLOEXEC before changing dumpable task
        flags

On 12/20, Aleksa Sarai wrote:
>
> @@ -1287,6 +1287,13 @@ void setup_new_exec(struct linux_binprm * bprm)
>  	/* This is the point of no return */
>  	current->sas_ss_sp = current->sas_ss_size = 0;
>  
> +	/*
> +	 * We have to apply CLOEXEC before we change whether the process is
> +	 * dumpable to avoid a race with a process in userspace trying to access
> +	 * the should-be-closed file descriptors of a process undergoing exec(2).
> +	 */
> +	do_close_on_exec(current->files);

Cosmetic, but perhaps this should go into flush_old_exec() then?

But I am fine either way, up to you.

Oleg.