From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x2247gX9QLbyYzd9ikk2945m8LsOlY90v4HTHVljCk973uXomoThQWTwIT4dK1XCyHG/CNf6p ARC-Seal: i=1; a=rsa-sha256; t=1517591847; cv=none; d=google.com; s=arc-20160816; b=A0LU0sSaFrsldub4sA1+mDuOfH+UdXnrfoQofAeqP5kxlDJ5LEdLHzn+7eDI4KDfP2 LGUcdtHDwGxvVIQhfaGexXLY+y7I8dU0ycEck5Ugzz/LO0lUA1VVdrLJ2peZMhEUhnjT VVhISwBinOn1Yotm6Ec29dpMkvbYpm0Tc30gNzeI9hvo1W7Uim6zFGNKejzpK3U5rXi/ t7ls2TYBHXUyatD4CptG0nEFzqg6YqddD/plv8yGItRxWwRohZzD+7z+SBUN3OmRnA74 O0pNg+8Uo2oW4Dm7EzHHCSYiu8o2fo9nTGpBI9RXgnkwu1VXYkTY9Aq+I5HlNb6sXxrv Bi/Q== 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=lvUh8SWgkK15wSAXtRdVW7V9N8tCmiZhbTKRd2QgxjI=; b=CD7FP1ohd/F39sJvJ2RAGFsUeeVy/T0wJ5TLK/yoUAI2KD64+rRibN6EtZ39IApjjR Uv1KQiu5QfD2SCUCWbyCHtx9QMyoARmErF0EctiAVLfRWlJbNDNyke8xQMQ9Xakqmqmo 6sZEvX/NspQoxbfHAd+hxNlh4PqnTXsfOIQHZwe1vE88OnSIy1kcHH1ujToTeuUfptfp OsEaOm3nfXzAnGjx+7EIc4ZAg3DHZr5M6tyTT4nlNP3+a5Go0UVMdtXXYBT/+yZ4kQxT y/k8qcoGj+OwAWpDaM3xyck6R01ikUtgsIudkbAjo5tFU4i3VdO8vO8n+5+wDdorI24w Af6A== 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 4.15 55/55] x86/efi: Clarify that reset attack mitigation needs appropriate userspace Date: Fri, 2 Feb 2018 17:59:13 +0100 Message-Id: <20180202140831.336212129@linuxfoundation.org> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180202140826.117602411@linuxfoundation.org> References: <20180202140826.117602411@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?1591310388977267326?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-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