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Ts'o" , Matthew Garrett Cc: Linus Torvalds , luto@kernel.org, David Howells , Ard Biesheuvel , jmorris@namei.org, Alan Cox , Greg Kroah-Hartman , Linux Kernel Mailing List , jforbes@redhat.com, linux-man@vger.kernel.org, jlee@suse.com, LSM List , linux-api@vger.kernel.org, Kees Cook , linux-efi Date: Wed, 04 Apr 2018 15:29:03 +0200 In-Reply-To: <20180404125743.GB16242@thunk.org> References: <20180404125743.GB16242@thunk.org> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.22.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K1:Qbe3Wk5lzvfzj44sUxQpaWNNbw2UugbIdlt5bt4k/uiI+xtOuGF Ga7Wk96MRLvxK3D9Q2RH3cEu8emEerZMoXsHhqCeXjVLWvcBKbDgzi/iBhOwqIfzKDke/aD Ny0PLJNrX74erPUtc+D+TTsntESY1T8oiqo+97hT6wM0Mny4fJhg5Wm/MWeq3SJ4dmG+dqt 0vuo4Yz57WI5DeGjiMwtQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:/z8YZcvgE8c=:JsoCnGlXBlH130FOQs4iHY 5Gca6UkPS/Zf3UGQ3nfTP/jDbSbp4pHvX7y2CENsa+Wun6W2fbaBVJ+iZvoDkISDufQ9hkrog qtIIUXQ+MAkBArtFuMiFL0BtF/fmMoa1qS7B/NnwkPd2ey4928gJklxFjlEn8YaTBUFIR1EC2 7Q1nO9TKHTTcI4soxOBM5Ut3/uyGks/tqk5SMEuAmjAZP6kC4JpgyhApPSkh3F8UC84+RV7pM GrDZxlSPycAZPEHJNFesDQci2QGiEnFMXRBobFcGJ39VGCXRPeS3O/ZTkphL57Od3nwB3nFTs pdZ59QxmhX/ieVs0q3aFArdJG97EXmlzB6YQy1WLyXitDj1uN+L2kFzfgVrkl0yqBNmZ8J7KF Bb8JE0K4Cd24QOgBRZm/mILYH1MjkQ29mUJMFScdLdDPa6b27KB8uLkI/M5AcZlQMH7sqoQy5 UVCmM9ld3oNuTHaqIkDrs/799CRn/a88Jwkhry5wGhacEbCFAruBWSQyjyau+xoM18dudUDHt 7PA53tpAGRKWTXg+GCwAnuCMeOMlQqxo9rz4rJ/SaOwF66TtqRwYOlmkiIdN65Iyk5hWmSEAu 8JGayqCCkBNLZaA0CA3Uaov0cu5qy3RfJfd0Rhm6/tzzjICjGtR2hB/LBBZoNeWzBkmXSGa19 meRxfdqcwchavrJ2JcBZ4mgXOQyAlSsF6LVTG04oQhSXIgdxUB9ZSrBwT/L8OLUxznJOU9xVC 8o4PAkc+WPm6IviShoMJY+gMUeItnxmPpIeJbgXPrnf8QolxjeDb8VVJQN8BPEc35FICqSa44 maTkicSJuInrTbcCDHIYfUzleMRG5+LcdICP7qYEHsQ6uijJ1k= Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, 2018-04-04 at 08:57 -0400, Theodore Y. Ts'o wrote: > On Wed, Apr 04, 2018 at 04:30:18AM +0000, Matthew Garrett wrote: > > What I'm afraid of is this turning into a "security" feature that ends up > > being circumvented in most scenarios where it's currently deployed - eg, > > module signatures are mostly worthless in the non-lockdown case because you > > can just grab the sig_enforce symbol address and then kexec a preamble that > > flips it back to N regardless of the kernel config. > > Whoa. Why doesn't lockdown prevent kexec? Put another away, why > isn't this a problem for people who are fearful that Linux could be > used as part of a Windows boot virus in a Secure UEFI context? > > If lockdown simply included a requirement for a signed kernel for > kexec --- and if kernel signing aren't available, to simply not alow > kexec, wouldn't that take care of this case? > > This wouldn't even be all that much of a burden for non-distro users > with lockdown enabled, since in my experience outside of enterprise > and data center use cases, kexec isn't used... Lots of folks use kdump, ergo kexec. -Mike