linux-kernel - Re: [PATCH 08/10] checkpatch: Remove awareness of uninitialized

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Message-ID: <202006031944.9551FAA68E@keescook>
Date:   Wed, 3 Jun 2020 19:44:53 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Joe Perches <joe@...ches.com>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Whitcroft <apw@...onical.com>, x86@...nel.org,
        drbd-dev@...ts.linbit.com, linux-block@...r.kernel.org,
        b43-dev@...ts.infradead.org, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org, linux-ide@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-spi@...r.kernel.org,
        linux-mm@...ck.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH 08/10] checkpatch: Remove awareness of
 uninitialized_var() macro

On Wed, Jun 03, 2020 at 06:47:13PM -0700, Joe Perches wrote:
> On Wed, 2020-06-03 at 18:40 -0700, Kees Cook wrote:
> > On Wed, Jun 03, 2020 at 05:02:29PM -0700, Joe Perches wrote:
> > > On Wed, 2020-06-03 at 16:32 -0700, Kees Cook wrote:
> > > > Using uninitialized_var() is dangerous as it papers over real bugs[1]
> > > > (or can in the future), and suppresses unrelated compiler warnings
> > > > (e.g. "unused variable"). If the compiler thinks it is uninitialized,
> > > > either simply initialize the variable or make compiler changes.
> > > > 
> > > > In preparation for removing[2] the[3] macro[4], effectively revert
> > > > commit 16b7f3c89907 ("checkpatch: avoid warning about uninitialized_var()")
> > > > and remove all remaining mentions of uninitialized_var().
> > > > 
> > > > [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
> > > > [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
> > > > [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
> > > > [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/
> > > 
> > > nack.  see below.
> > > 
> > > I'd prefer a simple revert, but it shouldn't
> > > be done here.
> > 
> > What do you mean? (I can't understand this and "fine by me" below?)
> 
> I did write "other than that"...
> 
> I mean that the original commit fixed 2 issues,
> one with the uninitialized_var addition, and
> another with the missing void function declaration.
> 
> I think I found the missing void function bit because
> the uninitialized_var use looked like a function so I
> fixed both things at the same time.
> 
> If you change it, please just remove the bit that
> checks for uninitialized_var.

Ah! Gotcha. Thanks; I will update it.

-Kees

> 
> Thanks, Joe
> 
> > > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > > []
> > > > @@ -4075,7 +4074,7 @@ sub process {
> > > >  		}
> > > >  
> > > >  # check for function declarations without arguments like "int foo()"
> > > > -		if ($line =~ /(\b$Type\s*$Ident)\s*\(\s*\)/) {
> > > > +		if ($line =~ /(\b$Type\s+$Ident)\s*\(\s*\)/) {
> > > 
> > > This isn't right because $Type includes a possible trailing *
> > > where there isn't a space between $Type and $Ident
> > 
> > Ah, hm, that was changed in the mentioned commit:
> > 
> > -               if ($line =~ /(\b$Type\s+$Ident)\s*\(\s*\)/) {
> > +               if ($line =~ /(\b$Type\s*$Ident)\s*\(\s*\)/) {
> > 
> > > e.g.:	int *bar(void);
> > > 
> > > Other than that, fine by me...
> > 
> > Thanks for looking it over! I'll adjust it however you'd like. :)
> > 
> 

-- 
Kees Cook