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

[DDD]

Rusty Russell wrote:
> On Sun, 21 Feb 2010 07:11:36 pm Américo 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 seemed useful to allow 'foo' as well as 'foo='. 

Ah, this is a good method to deal with this issue.

I will redo this patch shortly.

Thanks,
Dongdong

 But given these examples,
> obviously that was too easy to misuse.
>
> So I like your patch; please annotate it properly and put a comment
> like:
> 	/* We used to hand NULL for bare params, but most code didn't handle it :( */
>
> I assume none of those non-standard param parsers *want* to handle NULL?
>
> Thanks,
> Rusty.

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