From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 59BC1C98328 for ; Sat, 26 Sep 2026 06:48:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/ZtlgtRXx70iH42f7yzu0ahvdG98SNDqpIESzbWq6Cs=; b=sZO3TsctFRtqpbXU6w1iTuPena 1hBIMbphCxUHvaV0yv5cHPeljTrYkVNI4xeUT3O97OUH5wNj0v2lIG8wzJZqLfIwkE4cz/A6N94yW eaRk6AzzRTnYKMDNRm1alGZ6WCm6Q5y0SIxgPkmXjZ3TkBQ05MFkp9p/f6k/8/fFtZq96zqL0+lDN PTb0o48zQJyQdDALVthRkfRMd1LwaGB/BDrRUzmoTwb26P7XtGDs9ef/O+4JKRLLgGv7v3KjDE+fT pVyHbKXGSw9sNjS/cC6TaU4YmcsNgi3G0XzxF6rw4lBLYzcvO3xGrWTLSAg56H9oZmvNF1LBIu/Ol ESep06xg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xAMCe-0000000F5gp-0VVV; Sat, 26 Sep 2026 06:48:08 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xAMCb-0000000F5gf-3WY1; Sat, 26 Sep 2026 06:48:05 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 8E8FE6020C; Sat, 26 Sep 2026 06:48:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D5191F000FF; Sat, 26 Sep 2026 06:47:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790405284; bh=/ZtlgtRXx70iH42f7yzu0ahvdG98SNDqpIESzbWq6Cs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=K7hP34PKJi6Bjcv22MS8TIn+XW0Rx8BecEVNFElkjULeWp5il9FmTmLHnrmZjURsm MY4G/yFSo+VHJObjR7+6NyMJS/So7NLbCyIm5z3wbX9ZDaldB9bZxr8o2l6JTW1SP1 6svZup3jHwklut1SBhO1rWLTHK4uxE6WEIwRsyLDMs3Ah7CYv9BQ/tDG3rUmhoszL/ nh0r368reX/onFa7qh1GDmxQSQE/9gaWT8iwumST8Ty1lUAsrRwO1gPAkNXtXNGrRb 9A/PimWd4GasDWyRp82vXjmsfkojPF4x4FM8hU8HJRNWYavd1OdmlOr6/xw6hXpxms dTurdAJ5oUfYQ== Message-ID: Date: Sat, 26 Sep 2026 08:47:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arch, mm: promote DEBUG_WX to CHECK_WX To: "Mike Rapoport (Microsoft)" , Andrew Morton Cc: Albert Ou , Alexander Gordeev , Alexandre Ghiti , Borislav Petkov , Catalin Marinas , Christian Borntraeger , Dave Hansen , David Hildenbrand , Gerald Schaefer , Heiko Carstens , Ingo Molnar , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Mark Rutland , Michael Ellerman , Michal Hocko , Nicholas Piggin , Palmer Dabbelt , Paul Walmsley , "H. Peter Anvin" , Ritesh Harjani , Russell King , Shrikanth Hegde , Suren Baghdasaryan , Sven Schnelle , Thomas Gleixner , Vasily Gorbik , Vlastimil Babka , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org References: <20260925-direct-map-verify-wx-v1-1-7fd2f7d6d23b@kernel.org> Content-Language: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: <20260925-direct-map-verify-wx-v1-1-7fd2f7d6d23b@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Mike, Le 25/09/2026 à 11:53, Mike Rapoport (Microsoft) a écrit : > Verification that the kernel does not have writable + executable > mappings is about detecting security risks rather than a pure debug > feature. > > Major distribution configurations enable it in their kernels as well as > defconfigs of most architectures that have ARCH_HAS_DEBUG_WX. > > Rename relevant generic configuration options to use CHECK_WX and move > their definitions from mm/Kconfig.debug to mm/Kconfig. > > For arm that does not widely enable it, only rename its variants of the > config options. > > Enabling CHECK_WX adds a few kilobytes to the kernel binary and while > the added size can be slightly reduced with churny updates of > architecture implementations of ptdump, the core functionality takes > most of the added size. It cannot be moved to .init.text because the > verification has to happen after init sections are freed. > > With this, make generic CHECK_WX default to STRICT_KERNEL_RWX while > still leaving users targeting small kernels the possibility to opt-out. Looking at how it is done in powerpc I have some doubt with your reasoning. ptdump_check_wx() will report regardless of CONFIG_DEBUG_WX: if (st.wx_pages) { pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", st.wx_pages); return false; } else { pr_info("Checked W+X mappings: passed, no W+X pages found\n"); return true; } The only difference is we won't get the WARN_ONCE(): WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX), "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n", (void *)st->start_address, (void *)st->start_address); And I believe a big fat warning like this is a debug option not to be enabled on production kernels. So I think we should instead do: diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h index 240bd3bff18dd..714f63fb604a0 100644 --- a/include/linux/ptdump.h +++ b/include/linux/ptdump.h @@ -33,7 +33,7 @@ bool ptdump_check_wx(void); static inline void debug_checkwx(void) { - if (IS_ENABLED(CONFIG_DEBUG_WX)) + if (IS_ENABLED(CONFIG_PTDUMP)) ptdump_check_wx(); } That way you should get (untested) the following warning but not the big fat debug WARN(): Checked W+X mappings: FAILED, %lu W+X pages found Christophe