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Date: Wed, 18 Aug 2021 16:01:26 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: Kees Cook <keescook@...omium.org> Cc: linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] lkdtm/heap: Avoid __alloc_size hint warning On Tue, Aug 17, 2021 at 09:45:40PM -0700, Kees Cook wrote: > Once __alloc_size hints have been added, the compiler will > (correctly!) see this as an overflow. We are, however, trying to test > for this condition, so work around it with a volatile int. > > Signed-off-by: Kees Cook <keescook@...omium.org> > --- > drivers/misc/lkdtm/heap.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c > index 3d9aae5821a0..e59fcbe00ae0 100644 > --- a/drivers/misc/lkdtm/heap.c > +++ b/drivers/misc/lkdtm/heap.c > @@ -12,6 +12,8 @@ static struct kmem_cache *double_free_cache; > static struct kmem_cache *a_cache; > static struct kmem_cache *b_cache; > > +static volatile int __offset = 1; Perhaps a comment here as to why volatile is ok to use? That feels like it is a hack around the compiler of today, what happens tomorrow when newer versions decide to ignore volatile as it "knows" no one ever changes it? thanks, greg k-h
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