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Peter Anvin" , Linus Torvalds Subject: Re: [PATCH v1] x86/mm/pat: (un)track_pfn_copy() fix + improvements Message-ID: <4961949a-75db-4071-a478-fdc543c1dd28@stanley.mountain> References: <20250404124931.2255618-1-david@redhat.com> <630caa8e-2ee2-4895-9e4e-8bf2fa079100@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Apr 07, 2025 at 06:50:43PM +0200, Ingo Molnar wrote: > > diff --git a/mm/memory.c b/mm/memory.c > > index 2d8c265fc7d60..1a35165622e1c 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -1361,7 +1361,7 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) > > struct mm_struct *dst_mm = dst_vma->vm_mm; > > struct mm_struct *src_mm = src_vma->vm_mm; > > struct mmu_notifier_range range; > > - unsigned long next, pfn; > > + unsigned long next, pfn = 0; > > Ack. > > I hate it how uninitialized variables are even a thing in C, and why > there's no compiler switch to turn it off for the kernel. (At least for > non-struct variables. Even for structs I would zero-initialize and > *maybe* allow a non-initialized opt-in for cases where it matters. It > matters in very few cases in praxis. And don't get me started about the > stupidity that is to not initialize holes in struct members ...) Everyone sane uses CONFIG_INIT_STACK_ALL_ZERO these days. regards, dan carpenter