From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83056405C49 for ; Fri, 12 Jun 2026 17:40:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781286010; cv=none; b=oWWR63dk2daCPAzPOkNXIsyXmafMsoZrtRTT9WokJMTI8SncEE83z6F8oe1b1Ww+xchHR+gpPP0QIBBvTJYoGvBmpLSLyeElDPCA0fB6L2FibVqbBRC3ZXDNsBvnYbojJMAm28kySi74hv71tLqcaRadh5tRZHQPSpx2Aitv9jE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781286010; c=relaxed/simple; bh=uwje6irNV0DVSIq9D3ita3/M19mHMWGPm8MFY/Up0IQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bOZFwxXX8towG5JOGa36HUra22PQZ3QxygVsLMf7Oc30J0q997jjkOiC5FzmshAp7wteK7bTXaBlGcf1uMcVwfZU7qklZqBSdSYzAWRKhsSv2TQHadIQIUW4Xi1hj4G6GhZrSy3BNeJnjmDoXG4GkcOGriwIz0i5CIcu2TdHSak= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=lh+dpC7i; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="lh+dpC7i" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=iNJrx9oq1UL8pongmkdLsFBykQ7w2rMMq+Qfkkw31IU=; b=lh+dpC7iNTulzRVjZHkyI03ik0 aEN9yFJp5HpJJWZTqXtUyud760QbaIcR4iMK/+cF1e+V7h67crNPRJDqStJCyytj3YnbLSPkELaMu umSdzjpL6ThF0iH+JTh6XckNPbUSbX6s34lAxTcqhdQ2w1KHLKzahieF1UHJ1UobnfHqfdnVM2VHI biO35+CfthIWceH6bO2tGx4cCdDLEmmEWp80xUwYooL6mqWWGfWzcsmXUHsSI0VOJwDpky5RkuUq2 dYccoohxLfb7HrOqh/sZ62fFhr4nPy6yCqpwRFQrw6PERLR5DdP0RCcmdZNxw5oSB4LmQM1J8oE6S WlGNyBSg==; Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1wY5rI-0000000489n-1bAx; Fri, 12 Jun 2026 17:39:56 +0000 Date: Fri, 12 Jun 2026 18:39:56 +0100 From: Matthew Wilcox To: David Carlier Cc: akpm@linux-foundation.org, syzbot+fd95a72470f5a44e464c@syzkaller.appspotmail.com, David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kevin Tian , Jason Gunthorpe , Dave Hansen , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm: pgtable: protect lockless kernel page table walks with RCU Message-ID: References: <20260612091215.b06dc7dc9dc894a5bfc75429@linux-foundation.org> <20260612172356.356894-1-devnexen@gmail.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: <20260612172356.356894-1-devnexen@gmail.com> On Fri, Jun 12, 2026 at 06:23:55PM +0100, David Carlier wrote: > ptdump walks the kernel page tables locklessly through > walk_kernel_page_table_range_lockless(). It only holds the init_mm > mmap lock and the memory hotplug lock, and neither excludes > vmalloc/ioremap teardown from freeing kernel PTE pages via > pmd_free_pte_page() -> pagetable_free_kernel(). syzbot hit a > use-after-free in ptdump_pte_entry() reading a PTE page that was freed > underneath the walk. Does it make sense to walk the iomap / vmap ranges in ptdump? I can't really tell if this is something that's useful, or something that nobody thought to exclude.