From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227ANzSv5T1zdi4X6ib73JH6jQpllmRtEbLXqXfEukceuR8JKkAvxI8deNZPtea0alQKnjlt ARC-Seal: i=1; a=rsa-sha256; t=1517351215; cv=none; d=google.com; s=arc-20160816; b=AXNDpxP9X0NfM6tGGiO22P+W9egBqS13z3jklPDZltMUoQsPNgpYE5Ly2bAM+ZUt2o aNVfTEMVVmlytVGNTSR64pOmGVGSg5GZBGOL2jx7KXrcAp4+6tf86xfWOcMq1MzObxkd mKXjrKytmjKSFof4BdNzNHeehnYrtENFYlPR7wVYogvBcFIyO4ak8UeTxKHUYtTT2fEG MK1+Viw48B95qhu8X1GPVYVKiP4CgQ5WQtcbdvCCxc+IqF4GQx6jA/o4ObmWxkNHG2sn 6TACvHEg/001BjyM8qYn8IN3KyzIQPfNJDn8uTMTeP3uFoxUYM/JjIm5dEZNQHi09hQ7 t+8Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject :arc-authentication-results; bh=/H7I2SZbU/ZgEEIX5pNHZw+Zy9UU9Q/oAB0bYpoEWVM=; b=jEh0m6GbrWq/st5ycI4t4ca2dr+tD6RJcTg6mIS4raX/9N4c5QjXbks6AGmAD4cadK PzwQn/JE+/81SuvDgv8YRZxatcBSte0MG07fU3LY+YI3TQ8tp15hbGLHotCpAami3Uu+ Y43t+ZGbo3NAK6XrfunbIC7nXBr2WcWwJRHaNyQGU2eAscMQHb111sEoeptenufQL+ai Rhv+C/2I45pGrwzOCZ39ex5D/BFtqo7urZaIwMed7IJ4248ZnpTool5+CUBkOJZlDjDi J95hfzSA7i/blWU74hgpyqYLvb6/OoKVaD+g46rHzoV3GFb5201839O7Z9XAbyYl/+gV 1JXA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of tim.c.chen@linux.intel.com designates 192.55.52.136 as permitted sender) smtp.mailfrom=tim.c.chen@linux.intel.com Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of tim.c.chen@linux.intel.com designates 192.55.52.136 as permitted sender) smtp.mailfrom=tim.c.chen@linux.intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,436,1511856000"; d="scan'208";a="14679201" Subject: Re: [PATCH] x86/speculation: Use Indirect Branch Prediction Barrier in context switch To: Borislav Petkov Cc: David Woodhouse , arjan@linux.intel.com, tglx@linutronix.de, karahmed@amazon.de, x86@kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org, pbonzini@redhat.com, ak@linux.intel.com, torvalds@linux-foundation.org, gregkh@linux-foundation.org, mingo@kernel.org, luto@kernel.org, linux@dominikbrodowski.net References: <1517263487-3708-1-git-send-email-dwmw@amazon.co.uk> <20180130203836.bsgme6kf6hstgbrx@pd.tnic> <024dd53b-1912-34fa-deb8-550c111df521@linux.intel.com> <20180130215731.pszc5u4gcc32ds4v@pd.tnic> From: Tim Chen Message-ID: <296de30b-515b-6eab-1b13-bb2f71451004@linux.intel.com> Date: Tue, 30 Jan 2018 14:26:53 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <20180130215731.pszc5u4gcc32ds4v@pd.tnic> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590966106432961445?= X-GMAIL-MSGID: =?utf-8?q?1591058067969103841?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 01/30/2018 01:57 PM, Borislav Petkov wrote: > On Tue, Jan 30, 2018 at 01:03:20PM -0800, Tim Chen wrote: >> So it doesn't seem to be very practical attack if the victim has set >> itself to be non-dumpable. > > Probably, but considering how cheap our fix is, we might just as well > plug that hole too. > If the process has multiple threads running on different cpus, you will need to set IBPB on all cpus they are running in order to achieve your purpose. So it is not necessarily cheap. But I don't think it is really necessary. Tim