From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x224KbYm37fGMuy+/xCHjYq3GZ9esxeG+qjFO3ZaIZ0AH9/DFyk+ICUFldIeh3iUiEX9LVDjA ARC-Seal: i=1; a=rsa-sha256; t=1517591659; cv=none; d=google.com; s=arc-20160816; b=Np+eGAfW1DBZY/KbxFFWm4ve51CnoLF8kymZfpTVMp8K/6dZQoDXTES2O8Pdv39s09 MLP/G92Hy9BoNefXbLMyXFcyb9VcsOO6XxDRISiOoLuXvcp0W4+UcWXzTp8a481Gj9RV Yb+1ODIrUyP8EWm6aC+gS/kO05ykwssfWkjo+b1KZDSJ6rO/3xyVppG0fplnVTtzLHdb WdJ07kq8f47sbgRQSjHtwV6mKXRfEWs8LuS0lKJSkbCf91xzm+796RVBfwpknL/xK3KF N9+vLUGL8iD4QpQ/utFvFxtqTzH4/Jjz3IBbdF3D36SUuay8ckKhfUoBtX670EYOaRJq bZwQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=yuihUbh0XEAtraCEltfLhbLpxxwS9sqBp/ibIx393EM=; b=fAU4h6uv/n6uGquAv4welggfvvDzFNBvZKr2rqfI5e9HC8V7JDdOJh0zTBmx2e1WYV iutp/NgLMW6/wb4wn1lmvIb08/rXB8Qi/MCoaNeW9dRD44JrPpJJT/K+rIV71PRrhhX3 22w5kpsXxqYmS0xhkxegVUJZ9+aK51JnLxApboWV23u+CP8qHSdWr9Sc59MoGWnc+0bQ rWv9VY+cNDhIfPC80x/2c8Wm4Bk/rTq8MEotXO5+SKBkjP7Ieu7w86oxA5bLzueNcmbI sRTa2okZKFLH0PSvsNQLjsHxPiiwekF4ZEZ8yqwaBSdK13+pA6yzxAlV7RGf/qoNEUHk rhcw== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Matthew Garrett , Ard Biesheuvel , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , linux-efi@vger.kernel.org, Ingo Molnar Subject: [PATCH 4.14 156/156] x86/efi: Clarify that reset attack mitigation needs appropriate userspace Date: Fri, 2 Feb 2018 17:58:57 +0100 Message-Id: <20180202140847.458165935@linuxfoundation.org> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180202140840.242829545@linuxfoundation.org> References: <20180202140840.242829545@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1591310192231562942?= X-GMAIL-MSGID: =?utf-8?q?1591310192231562942?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Matthew Garrett commit a5c03c31af2291f13689d11760c0b59fb70c9a5a upstream. Some distributions have turned on the reset attack mitigation feature, which is designed to force the platform to clear the contents of RAM if the machine is shut down uncleanly. However, in order for the platform to be able to determine whether the shutdown was clean or not, userspace has to be configured to clear the MemoryOverwriteRequest flag on shutdown - otherwise the firmware will end up clearing RAM on every reboot, which is unnecessarily time consuming. Add some additional clarity to the kconfig text to reduce the risk of systems being configured this way. Signed-off-by: Matthew Garrett Acked-by: Ard Biesheuvel Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- drivers/firmware/efi/Kconfig | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -159,7 +159,10 @@ config RESET_ATTACK_MITIGATION using the TCG Platform Reset Attack Mitigation specification. This protects against an attacker forcibly rebooting the system while it still contains secrets in RAM, booting another OS and extracting the - secrets. + secrets. This should only be enabled when userland is configured to + clear the MemoryOverwriteRequest flag on clean shutdown after secrets + have been evicted, since otherwise it will trigger even on clean + reboots. endmenu