Re: [PATCH wireless 0/9] wifi: cfg80211: avoid some garbage values

[Arend Van Spriel]

On July 2, 2024 4:02:39 PM Jonas Gorski <jonas.gorski@xxxxxxxxx> wrote:

> Hi,
>
> On Tue, 2 Jul 2024 at 14:50, Su Hui <suhui@xxxxxxxxxxxx> wrote:
> > Clang static checker (scan-build) has some warnings as follows.
> >
> > included from drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.c:16
> > drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil.h:123:2:
> > warning:Assigned value is garbage or undefined [core.uninitialized.Assign]
> > 123 |         __le32 data_le = cpu_to_le32(*data);
> > |         ^~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~
> > drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.c:138:3:warning
> > Value stored to 'err' is never read [deadcode.DeadStores]
> >
> > There are some functions like brcmf_fil_{cmd,iovar,basscfg}_int_get()
> > which read the value of its parameter, but some callers have not
> > initialized these parameters which will be read. And this patchset fixes
> > these problems.
>
> The core issue here seems to be that
> brcmf_fil_{cmd,iovar,basscfg}_int_get() function (needlessly?) read
> from *data.
>
> So instead of forcing all callers of
> brcmf_fil_{cmd,iovar,basscfg}_int_get() to initialize *data first, I
> suggest changing brcmf_fil_{cmd,iovar,basscfg}_int_get() to just not
> read from it.
>
> I see no reason why they should care about what the previous value
> was, since they are supposed to overwrite it anyway.

The issue here is that these are generic functions and there is a reason. 
Some firmware API primitives allow/require the caller to pass selection 
parameters in *data. We wanted to keep the functions generic and leave out 
that knowledge. I suppose we could introduce a separate set of api 
functions for that purpose, but it seems like significant overhead to 
silence compiler warnings. Guess I underestimate the potential risk of 
leaking few bytes of stack data.


Regards,
Arend

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