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[67.164.59.41]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-24b0e860ab5sm32663555ad.5.2025.09.02.13.06.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Sep 2025 13:06:07 -0700 (PDT) Date: Tue, 2 Sep 2025 13:06:05 -0700 From: "Vishal Moola (Oracle)" To: David Hildenbrand Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Kees Cook , kernel test robot , Dan Carpenter Subject: Re: [PATCH] mm: Fix kernel stack tagging for certain configs Message-ID: References: <20250902175903.1124555-1-vishal.moola@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: F4101160012 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: yhdtp71o7er7zq7euitbs9fgiwxopxrc X-HE-Tag: 1756843569-216518 X-HE-Meta: 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 x2crX/Uf WT+v9iAQnb6uOdIb61ob3tjVe3WEZZecHdFDTqZQn+0tyzYHkhNMOQl9Mh/2NPTrKJ1BDs4BlJDsJabb4FcKB0a8giC0jUlOurbHhHP5SQsbe71lCXtvJahPydBlPLLPkrXTrccv07sIyFSHwukJt7pT+t6292ZZAhJFQV+cqzbdcJZhVuExDfBtG4xyWTfGw7CIaX+V2qklXXKrFAO96ku4f01GgjrcPdoc9myAex2D3yCC5I/RZUifohDXi87dRpDis8vfOkiGeobCOqh6mvIA22OkT3qdq2VYICkOnuZXpqWq7MDkhDPXt2Tt869UZlVtQ7fzqF2Qmy3NLE0YDxnHssQUi62cez8PytDUEVcaU3eVXmQh6yiSJndbbBm4BQQ/vonnrGwe+Tb5d87hygWvXSHDCeHgRLqK8NOxivH3VmzTBWm7Mxh9WBz/QSmuubHmo7XJ9Zq9Ut3Gi1pJ70JlaIcClJiuvHGUy+HPdRhzv8aIB+q6Rcpzu9f/M7AMRTuYyr8s0XPpNHYhWDxhpBd8J86nBvrelFUqGPMOdDLMyONWW+1bULEkm99+GYdek7S72x8lo3MNQB4Y5EvHDhTYfVQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 02, 2025 at 08:23:06PM +0200, David Hildenbrand wrote: > On 02.09.25 19:59, Vishal Moola (Oracle) wrote: > > Commit 4ef905bda61f ("mm: tag kernel stack pages") began marking pages > > that were being used for the kernel stack. > > > > 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. > > > > 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. > > > > We definitely have at least 1 page we want tagged at this point, so fix > > it by using a do {} while loop instead of a for loop. > > > > Fixes: 4ef905bda61f ("mm: tag kernel stack pages") > > Reported-by: kernel test robot > > Reported-by: Dan Carpenter > > Closes: https://lore.kernel.org/r/202508300929.TrRovUMu-lkp@intel.com/ > > Signed-off-by: Vishal Moola (Oracle) > > --- > > You sent the patch on August 20 and I replied on August 21. > > I did not receive any reply so far. Ah sorry, I didn't mean to miss your reply. I can't find your reply in my inboxes so I definitely missed it somehow. I'll go find it and respond. > And now I realize that this patch is not upstream yet and the commit id not > stable. So the Fixes/Closes etc. do not really apply. Gotcha. > My current opinion is that we don't want this. (see vmalloc reasoning and > unclear use) > > I'm happy to be convinced otherwise. > > -- > Cheers > > David / dhildenb >