linux-kernel - Re: [PATCH] module param_call: fix potential NULL pointer dereference

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Message-ID: <2375c9f91002210041l1bf30871vdf3881589a654d5a@mail.gmail.com>
Date:	Sun, 21 Feb 2010 16:41:36 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Dongdong Deng <dongdong.deng@...driver.com>
Cc:	rusty@...tcorp.com.au, davem@...emloft.net,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	jason.wessel@...driver.com, lenb@...nel.org, dwmw2@...radead.org,
	mdharm-usb@...-eyed-alien.net, bfields@...ldses.org,
	robert.richter@....com
Subject: Re: [PATCH] module param_call: fix potential NULL pointer dereference

On Sun, Feb 21, 2010 at 3:24 PM, Dongdong Deng
<dongdong.deng@...driver.com> wrote:
> The param_set_fn() function will get a parameter which is a NULL
> pointer when insmod module with params via following method:
>
> $insmod module.ko module_params
>
> BTW: the normal method usually as following format:
> $insmod module.ko module_params=example
>
> If the param_set_fn() function didn't check that parameter and used
> it directly, it could caused an OOPS due to NULL pointer dereference.
>
> The solution is simple:
> Just checking the parameter before using in param_set_fn().
>
> Example:
> int set_module_params(const char *val, struct kernel_param *kp)
> {
>        /*Checking the val parameter before using */
>        if (!val)
>                return -EINVAL;
>        ...
> }
> module_param_call(module_params, set_module_params, NULL, NULL, 0644);
>

Why not just checking all of them in the generic code?
How about my _untested_ patch below?

Thanks.

-----------

When a module parameter "foo" is not bool, we shouldn't accept arguments
like this "insmod ./foo.ko foo". However, currently only standard
->set functions
check this, several non-standard ->set functions ignore this, thus could cause
NULL def oops.

Reported-by: Dongdong Deng <dongdong.deng@...driver.com>
Signed-off-by: WANG Cong <xiyou.wangcong@...il.com>

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View attachment "kernel-params_c-check-null-for-non-bool.diff" of type "text/plain" (461 bytes)