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

[DDD]

AmÃrico Wang wrote:
> 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)
> > {
> >        /*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?

It is no problem that we check the params before invoking param_set_fn().

But I trend to do the checking in param_set_*fn(), because we can offer 
some special prompt infos to user if we want and handle some special 
cases like param_set_bool().

Thanks,
Dongdong


> 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>
>
> ---

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