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[198.145.29.99]) by mx.google.com with ESMTPS id i26-v6si7885316pgn.433.2018.05.28.03.36.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 May 2018 03:36:34 -0700 (PDT) Received-SPF: pass (google.com: domain of srs0=wbis=ip=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=gNudSAI8; spf=pass (google.com: domain of srs0=wbis=ip=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=WbIs=IP=linuxfoundation.org=gregkh@kernel.org Received: from localhost (LFbn-1-12247-202.w90-92.abo.wanadoo.fr [90.92.61.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 55BAA208AE; Mon, 28 May 2018 10:36:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1527503794; bh=ZL/IUvGzxXWPTJTBinEGDSKlgM8Rs6SNe/qh+pecxAU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gNudSAI80A51iqyHYuXrZu9MR+rZ2FgA6aKtIRLS/46zNyfbIig5FhBWNYxzlGOeL l2heNO+26zDfarUtMO6sWNR1QDB/sRk20YNdezeNSgO5N9pv7VtIdJyIrdNsxv/zNp fCSQi7HBXKnu3zqygi+4PyBoIzZ1q3lJbxOXmGpI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dave Hansen , Kees Cook , Andrea Arcangeli , Andy Lutomirski , Arjan van de Ven , Borislav Petkov , Dan Williams , David Woodhouse , Hugh Dickins , Josh Poimboeuf , Juergen Gross , Linus Torvalds , Nadav Amit , Peter Zijlstra , Thomas Gleixner , linux-mm@kvack.org, Ingo Molnar , Sasha Levin Subject: [PATCH 4.9 231/329] x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init Date: Mon, 28 May 2018 12:02:40 +0200 Message-Id: <20180528100301.329900202@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180528100241.796630982@linuxfoundation.org> References: <20180528100241.796630982@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 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: X-Virus-Scanned: ClamAV using ClamSMTP 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dave Hansen [ Upstream commit 639d6aafe437a7464399d2a77d006049053df06f ] __ro_after_init data gets stuck in the .rodata section. That's normally fine because the kernel itself manages the R/W properties. But, if we run __change_page_attr() on an area which is __ro_after_init, the .rodata checks will trigger and force the area to be immediately read-only, even if it is early-ish in boot. This caused problems when trying to clear the _PAGE_GLOBAL bit for these area in the PTI code: it cleared _PAGE_GLOBAL like I asked, but also took it up on itself to clear _PAGE_RW. The kernel then oopses the next time it wrote to a __ro_after_init data structure. To fix this, add the kernel_set_to_readonly check, just like we have for kernel text, just a few lines below in this function. Signed-off-by: Dave Hansen Acked-by: Kees Cook Cc: Andrea Arcangeli Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Dan Williams Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: Hugh Dickins Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Nadav Amit Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180406205514.8D898241@viggo.jf.intel.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/pageattr.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -279,9 +279,11 @@ static inline pgprot_t static_protection /* * The .rodata section needs to be read-only. Using the pfn - * catches all aliases. + * catches all aliases. This also includes __ro_after_init, + * so do not enforce until kernel_set_to_readonly is true. */ - if (within(pfn, __pa_symbol(__start_rodata) >> PAGE_SHIFT, + if (kernel_set_to_readonly && + within(pfn, __pa_symbol(__start_rodata) >> PAGE_SHIFT, __pa_symbol(__end_rodata) >> PAGE_SHIFT)) pgprot_val(forbidden) |= _PAGE_RW;