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

[AmÃrico Wang]

On Sun, Feb 21, 2010 at 3:24 PM, Dongdong Deng
<dongdong.deng@xxxxxxxxxxxxx> 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)
> {
> Â Â Â Â/*Checking the val parameter before using */
> Â Â Â Âif (!val)
> Â Â Â Â Â Â Â Âreturn -EINVAL;
> Â Â Â Â...
> }
> 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@xxxxxxxxxxxxx>
Signed-off-by: WANG Cong <xiyou.wangcong@xxxxxxxxx>

---
diff --git a/kernel/params.c b/kernel/params.c
index cf1b691..84a1466 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -59,6 +59,8 @@ static int parse_one(char *param,
 	/* Find parameter */
 	for (i = 0; i < num_params; i++) {
 		if (parameq(param, params[i].name)) {
+			if ((!params[i].flags & KPARAM_ISBOOL) && !val)
+				return -EINVAL;
 			DEBUGP("They are equal!  Calling %p\n",
 			       params[i].set);
 			return params[i].set(val, &params[i]);