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Peter Anvin" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jennifer Miller , Tiffany Bao , Ruoyu Wang , Adam Doupe , Kyle Zeng , Yan Shoshitaishvili Subject: Re: [PATCH v2] mm/vmalloc: widen guard region to defeat ENTER-based stack pivot Message-ID: <20260701072351.GM48970@noisy.programming.kicks-ass.net> References: <20260629214712.1198680-1-xmei5@asu.edu> <4e96acf4-25e7-4f30-8455-f9b3f49062be@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 6A696100010 X-Stat-Signature: kkjhjb76r3nnjxbn3c9zjpd78hueuac1 X-HE-Tag: 1782890637-681323 X-HE-Meta: U2FsdGVkX193KlGhAwP+hD+Ct9DXRG2OWVh56RfirxHhBUih4ibUZF+7J4w748C8DbfRCjIWM4luGR0hmSVseziGqtqQ9FhkEgwvHwoInkDzOkTH+THkP2JlDb24nnVIyXo0Q5DmEzIFpAySIh8pxPELWSH1bRJnlTw3FYUzf9bGUPE4Gw6JjYTLAhlWrMFVPJHjd0VfRPSYGOttzHf76oLoRZlwM0C84A7V/snMxbLSbGupQ1Hxac7D84sdrslMFS/PJO94IWkhWPklIqU9AynqGrTZM4JjCb4Qh+EvCsdrEhEc7fcnNJiOrHh0abBexHulF2gnbePB/tx4lKt5qXFDZtIjf3Xgk1lLYlZ1MvZIdFSzvZCj3TFsGcG9i3EoNqvJ/gfh+KcKR6jKfPlXrouRDLFeVuv48AbSsYvvzspaVhIVGiureFbBUscYu/QmooatjcDNALGEmBRjDel1yvdJSa42Yo2GcSmrCIQE4Q52xrB4WTBk8vnG2QRXooQi1HBaFnMd/5tLrdp4eJyZFqRyL9ylVNW4eahOGf3ReBo+pwOxA5QZCV4MnPj2/4o/OPonFiO+B1HoJiOziUc2Life3T22z2PtQeYOvzUtrAqfwF7Cv0z4AgVTl//MLzCX9bcK22hImqUMjXzDEKQ3uI7DYNlCb0q2HIBjdezNRgR8ePnrj6CnktOjeWdHXAhYIhQXlZXGFW8kFdlhGVIFpfm0Wr6NJ2W9MRc9w6MY7OEy1qkanCouI8GUV1WjSWWM9qos1GXj97Kzn+nTyhdult5G7wgMXvt1C5uKqPkbOpbia2gwIDapWAAKxTy/N2FXYTSm1+0/jZftrrjbL54tSGRnP4jIc9nmen9vHkE2c4AFoTZ3P0jt5DZl79NlMtKKGn73mlEhTfuGRKE9jbhWMVgsVkbJ/bg9GhvgzvdZxmfnfL0wg9n+by7rZ9RKNY687perSqALy13vhbe20Fv JTDcA0Oa A+L4WSn1Iaxytw2bxP/fRUBnI2VyXWOLrwPRKIKwpWhrV2znqHaHGMIUYan0Sohf+bdQVGmOAuXFxR6wP16idwg8lQ9CTQa3SlRzYVkT3KaH5BCc5w/Gd123m3hczrTLUa3qt3CpyZfuRe+qixAqXpA8HUBNr4Rj8Gh8Hzrr3ahdVAO2Ag7coZqmdnX3PJ4Jcxe3iNvT6kGU/9l02R4bJlr19fGnZkQPM3aKFOdSOF/iHClwjSaRZQC0xiScxeVlohQCJ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 30, 2026 at 03:58:41PM +0100, Pedro Falcato wrote: > On Tue, Jun 30, 2026 at 07:01:48AM -0700, Dave Hansen wrote: > > On 6/29/26 18:22, Xiang Mei wrote: > > >> Please don't even try to send a v3 without addressing this. > > > This is a demo exploiting CVE-2026-31419 with this technique: > > > https://github.com/google/security-research/pull/397 > > > > Thanks for sharing that. That's really good info. > > > > But what I want to hear a bit more about is why this new guard region is > > a good, generic mitigation. Does it help mitigate a whole class of > > vulnerabilities? > > I guess, to add to the questions (to Xiang and/or x86 people): > 1) Aren't initiatives like kCFI/CET/shadow stack supposed to mitigate these > issues? Is this mitigation supposed to be applied in spite of these features? > 2) Aren't you screwed by the time the attacker gets kernel remote code > execution anyway? Right; so CFI is supposed to eliminate the forward control flow hijacking primitives, and shadow-stack will hobble the backward ones. The whole ENTER thing is really only relevant provided you have a control flow hijack of some sort. Once you do, it makes it easier to build out a ROP chain.