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Tue, 02 Sep 2025 13:09:40 -0700 (PDT) Date: Tue, 2 Sep 2025 23:09:37 +0300 From: Dan Carpenter To: Matthew Wilcox Cc: "Vishal Moola (Oracle)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Kees Cook , kernel test robot 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-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A31BF2000E X-Stat-Signature: 8bui57upy3an91m7hemumr15pworxbnu X-HE-Tag: 1756843782-597370 X-HE-Meta: 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 FvRJem8B twAGaBK8GcF/568ykHV4PN5AJvvmgezIlQz0o+g0NiB9Fn+ReND3bFOkeQQIqXViKvju+1/i45enMPxmnG/hcbvacSKWAPOq6IyMTQbD2OJklP5Rlna89/hjMiYruWiPbceBk23YTom/9wNVloJZ9gxrmojHBN/tmXsr7qPPuTU09qZE3itGa+MGVbyFhYUA+L6VpDZRQGom/r5X4VofWzbHMjiPWo0x0IiWktsRMXm/tpcuG7k8S7ljVBLqLwAgDCoPRG3xoTdjY6ZLPpEu1ltySstwWw/UOtY9jHMrOs7dXsZGB5eisINBybsaCEQ98urpxWpzMZKdTLSs+vRll75WMy9L069rFsqLfXH9inUczJ+YTYjRlsyUQuxahFjL5JaurMn08AWmb2EA= 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 08:30:14PM +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