linux-kernel - Re: [PATCH 1/1] usermodehelper: check subprocess

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Message-ID: <CAKi4VAKj+s0Z9QHfqwG3+y33puL4dVaou5ys+eiD-yLf8h5QrA@mail.gmail.com>
Date:	Thu, 16 May 2013 13:16:08 -0300
From:	Lucas De Marchi <lucas.de.marchi@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Colin Walters <walters@...bum.org>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Jiri Slaby <jslaby@...e.cz>,
	Lennart Poettering <mzxreary@...inter.de>,
	Neil Horman <nhorman@...driver.com>, security@...nel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] usermodehelper: check subprocess_info->path != NULL

Hi Oleg,

On Thu, May 16, 2013 at 12:43 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> argv_split(empty_or_all_spaces) happily succeeds, it simply returns
> argc == 0 and argv[0] == NULL. Change call_usermodehelper_exec() to
> check sub_info->path != NULL to avoid the crash.
>
> This is the minimal fix, todo:
>
>         - perhaps we should change argv_split() to return NULL or
>           change the callers.

Changing argv_split() would be the easiest way, but then we can't
differentiate the errors. Right now it returns NULL only on ENOMEM.


>
>         - kill or justify ->path[0] check

I'm not sure about this, it's already there before my refactor and I
don't think it makes any good. From modprobe pespective, I'd say it
would be better to give an error than say everything went ok.


>
>         - narrow the scope of helper_lock()
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> Cc: stable@...r.kernel.org
> ---
>  kernel/kmod.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/kmod.c b/kernel/kmod.c
> index 1296e72..8241906 100644
> --- a/kernel/kmod.c
> +++ b/kernel/kmod.c
> @@ -569,6 +569,11 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
>         int retval = 0;
>
>         helper_lock();
> +       if (!sub_info->path) {
> +               retval = -EINVAL;
> +               goto out;
> +       }
> +
>         if (sub_info->path[0] == '\0')
>                 goto out;
>
> --

Acked-By: Lucas De Marchi <lucas.demarchi@...el.com>


Lucas De Marchi
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