linux-kernel - Re: [PATCH] mm: Fix kernel stack tagging for certain configs

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Message-ID: <aLdPAa54rrZsOFm_@stanley.mountain>
Date: Tue, 2 Sep 2025 23:09:37 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: "Vishal Moola (Oracle)" <vishal.moola@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Kees Cook <kees@...nel.org>, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] mm: Fix kernel stack tagging for certain configs

On Tue, Sep 02, 2025 at 08:30:14PM +0100, Matthew Wilcox wrote:
> On Tue, Sep 02, 2025 at 10:59:03AM -0700, Vishal Moola (Oracle) wrote:
> > There are 3 cases where kernel pages are allocated for kernel stacks:
> > CONFIG_VMAP_STACK, THREAD_SIZE >= PAGE_SIZE, THREAD_SIZE < PAGE_SIZE.
> > These cases use vmalloc(), alloc_pages() and kmem_cache_alloc()
> > respectively.
> 
> I missed that the third case existed ...
> 
> > In the first 2 cases, THREAD_SIZE / PAGE_SIZE will always be greater
> > than 0, and pages are tagged as expected. In the third case,
> > THREAD_SIZE / PAGE_SIZE evaluates to 0 and doesn't tag any pages at all.
> > This meant that in those configs, the stack tagging was a no-op, and led
> > to smatch build warnings.
> 
> I didn't see those smatch warnings.  Were they cc'd to the mailing list?
> 

I messed up and accidentally sent an email with two Message-ID headers
so maybe it got eaten by your spam filter?

https://lore.kernel.org/all/202508300929.TrRovUMu-lkp@intel.com/

regards,
dan carpenter