Re: [PATCH v3 5/6] staging: r8188eu: add error handling of rtw_read32

Pavel Skripkin
2021-08-26T20:03:08Z

On 8/26/21 1:59 PM, David Laight wrote:
> From: Pavel Skripkin
>> Sent: 26 August 2021 11:55
>>
>> On 8/26/21 1:22 PM, David Laight wrote:
>> > From: Pavel Skripkin
>> >> Sent: 26 August 2021 10:28
>> >>
>> >> On 8/26/21 12:22 PM, Pavel Skripkin wrote:
>> >> > On Thu, 26 Aug 2021 08:51:23 +0000
>> >> > David Laight <David.Laight@ACULAB.COM> wrote:
>> > ...
>> >> >> ...
>> >> >> > -static u32 usb_read32(struct intf_hdl *pintfhdl, u32 addr)
>> >> >> > +static int usb_read32(struct intf_hdl *pintfhdl, u32 addr, u32
>> >> >> > *data) {
>> >> >> > u8 requesttype;
>> >> >> > u16 wvalue;
>> >> >> > u16 len;
>> >> >> > - __le32 data;
>> >> >> > + int res;
>> >> >> > + __le32 tmp;
>> >> >> > +
>> >> >> > + if (WARN_ON(unlikely(!data)))
>> >> >> > + return -EINVAL;
>> >> >> >
>> >> >>
>> >> >> Kill the NULL check - it is a silly coding error.
>> >> >> An OOPS is just as easy to debug.
>> >> >>
>> >> >
>> >> >
>> >> > I don't think that one single driver should kill the whole system. It's
>> >> > 100% an error, but kernel can recover from it (for example disconnect
>> >> > the driver, since it's broken).
>> >> >
>> >> >
>> >> > AFIAK, Greg and Linus do not like BUG_ONs in recoverable state...
>> >> > Correct me, if I am wrong
>> >> >
>> >> Oops, I thought about BUG_ON() instead of WARN_ON(), sorry for
>> >> confusion. My point is "we should not let the box boom".
>> >
>> >
>> > There is no point checking for NULL that just can't happen.
>> > In this case all the callers will pass the address of a local.
>> > There really is no point checking.
>> >
>>
>> We not always read in local variable, there are few places, where we
>> read into passed buffer.
>
> It is still a very local coding bug.
>
> David
>

Sure, but is defensive programming so bad?

Greg, what your opinion about this NULL check?

With regards,
Pavel Skripkin