netdev - Re: [PATCH] rt2x00: reset reg earlier in rt2500usb_register

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Message-ID: <CAD-N9QWao8+VFLbE00Dmo0Kpwf2ATzaP=F=QWk=5R8Td_JWsew@mail.gmail.com>
Date:   Thu, 21 Jan 2021 19:25:31 +0800
From:   慕冬亮 <mudongliangabcd@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     davem@...emloft.net, helmut.schaa@...glemail.com,
        kvalo@...eaurora.org, linux-kernel <linux-kernel@...r.kernel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        sgruszka@...hat.com
Subject: Re: [PATCH] rt2x00: reset reg earlier in rt2500usb_register_read

On Thu, Jan 21, 2021 at 7:21 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Thu, Jan 21, 2021 at 06:59:08PM +0800, 慕冬亮 wrote:
> > > >       rt2x00usb_vendor_request_buff(rt2x00dev, USB_MULTI_READ,
> > > >                                     USB_VENDOR_REQUEST_IN, offset,
> > > >                                     &reg, sizeof(reg));
> > >
> > > Are you sure this is valid to call this function with a variable on the
> > > stack like this?  How did you test this change?
> >
> > First, I did not do any changes to this call. Second, the programming
> > style to pass the pointer of stack variable as arguments is not really
> > good. Third, I check this same code file, there are many code snippets
> > with such programming style. :(
>
> I know you did not change it, what I am asking is how did you test this
> change works?  I think the kernel will warn you in huge ways that using
> this pointer on the stack is incorrect, which implies you did not test
> this change :(
>

I tested this patch only with PoC. The patched kernel version did not
crash when executing the PoC.

BTW, I did not take notice of the warning information as there are
many many warnings in building KMSAN.

> thanks,
>
> greg k-h