linux-hardening - Re: [PATCH 2/5] slab: Add __alloc_size attributes for better bounds checking

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Date:   Wed, 18 Aug 2021 18:10:57 -0700
From:   Joe Perches <joe@...ches.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Jonathan Corbet <corbet@....net>,
        linux-doc <linux-doc@...r.kernel.org>
Cc:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
        Daniel Micay <danielmicay@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        clang-built-linux@...glegroups.com, linux-kbuild@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 2/5] slab: Add __alloc_size attributes for better bounds
 checking

On Thu, 2021-08-19 at 01:27 +0100, Matthew Wilcox wrote:
> On Tue, Aug 17, 2021 at 10:31:32PM -0700, Joe Perches wrote:
> > Lastly __alloc_size should probably be added to checkpatch
> > 
> > Maybe:
> > ---
> >  scripts/checkpatch.pl | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> > @@ -489,7 +489,8 @@ our $Attribute	= qr{
> >  			____cacheline_aligned|
> >  			____cacheline_aligned_in_smp|
> >  			____cacheline_internodealigned_in_smp|
> > -			__weak
> > +			__weak|
> > +			__alloc_size\s*\(\s*\d+\s*(?:,\s*d+\s*){0,5}\)
> 
> Should probably be added to kernel-doc as well.  Any other awful regexes
> that need to be changed to understand it?  And can we commonise the
> regexes that do exist into a perl helper library?

probably, but there would need to be some library work done and
changes made to both utilities so they could use the same $helpers.

And there are several nominally incomplete regexes already in
kernel-doc and I'm not at all familiar with kernel-doc.

e.g.: kernel-doc has:

my $attribute = qr{__attribute__\s*\(\([a-z0-9,_\*\s\(\)]*\)\)}i;

but __attribute__ can have quotes like:

__attribute__((section("foo")))

and spaces around and and I believe between (( and )) like:

__attribute__ ((packed))

so those wouldn't match.

The use of parentheses internal to attributes like __align__(8) may
not work particularly well either given greedy matching.