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Mon, 07 Apr 2025 00:11:28 -0700 (PDT) Received: from localhost ([196.207.164.177]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-43ec16a3aefsm124095515e9.21.2025.04.07.00.11.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Apr 2025 00:11:27 -0700 (PDT) Date: Mon, 7 Apr 2025 10:11:24 +0300 From: Dan Carpenter To: David Hildenbrand Cc: Lorenzo Stoakes , kernel test robot , oe-kbuild@lists.linux.dev, Dan Carpenter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Liam R. Howlett" , x86@kernel.org Subject: Re: [PATCH v3] x86/mm/pat: Fix VM_PAT handling when fork() fails in copy_page_range() Message-ID: <202ba609-277d-4f16-92df-8a5a94f99ad4@stanley.mountain> References: <94c35e89-f915-4122-b1a0-436893201373@stanley.mountain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 0102F40005 X-Stat-Signature: zr83ihioayfyg6rhu4nyrswn6k4mr6bb X-HE-Tag: 1744009889-914315 X-HE-Meta: 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 wl3TWgKc t+wo8qSV6/rYd3sGeeHp6E35cZx/E0U3mTY3KT6zg03RNuhrlrUuYU514pQRUzaASoM4ejG0/wDKqk4MaU3v0T4iP9GPwI4klsZOdxPHPAI8YXMjbz2mFFfGmLB2AG6W+JmZR7/uxVaHdzx1iksqnnlvAmR3luLnmphjNc6cysvHVqBATc9WhcXa1at55wsrXa47c52uKBG4xHSUeVl1UuYbsmfYwro6iR3cexVqUFVizDhjPgf40dhr47UY5tpOiI/GXGEg8B2olWP2yf79TY4JrsnNzo/7jAzvB2Qvue1/B6Ezq/Abj+kCigDKPLPdNgn3P X-Bogosity: Ham, tests=bogofilter, spamicity=0.000029, 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 Thu, Apr 03, 2025 at 10:59:12PM +0200, David Hildenbrand wrote: > On 03.04.25 17:14, Dan Carpenter wrote: > > Sorry, I've been having trouble with my email recently... I replied > > earlier but my email got eaten on the way out. > > > > What happened here is that the zero day bot emails go to me first and > > then I review them or forward them depending on if they're a real > > issue or not. > > > > Here it's a false postive because it's set and used if the > > (src_vma->vm_flags & VM_PFNMAP) flag is set. Smatch doesn't parse > > this correctly. I've been meaning to fix this in Smatch for a > > while. > > There is a slight complication (on top of the VM_PFNMAP checks): > > If "src_vma->vm_flags & VM_PAT" we > * set pfn > * set dst_vma->vm_flags |= VM_PFNMAP > > Then, we only consume the pfn if "dst_vma->vm_flags & VM_PFNMAP" > > While we won't be using the uninitialized pfn (good), we'd still pass an > uninitialized pfn, which IIRC is UB; likely nothing happens on GCC clang, > but we better handle it. Passing an uninitialized variable is UB, but if the function is inlined then it's fine. regards, dan carpenter