Date: Tue, 9 May 2017 08:56:19 +0200 From: Ingo Molnar <mingo@...nel.org> To: Kees Cook <keescook@...omium.org> Cc: Daniel Micay <danielmicay@...il.com>, Thomas Garnier <thgarnie@...gle.com>, Martin Schwidefsky <schwidefsky@...ibm.com>, Heiko Carstens <heiko.carstens@...ibm.com>, Dave Hansen <dave.hansen@...el.com>, Arnd Bergmann <arnd@...db.de>, Thomas Gleixner <tglx@...utronix.de>, David Howells <dhowells@...hat.com>, René Nyffenegger <mail@...enyffenegger.ch>, Andrew Morton <akpm@...ux-foundation.org>, "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>, "Eric W . Biederman" <ebiederm@...ssion.com>, Oleg Nesterov <oleg@...hat.com>, Pavel Tikhomirov <ptikhomirov@...tuozzo.com>, Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>, Rik van Riel <riel@...hat.com>, Josh Poimboeuf <jpoimboe@...hat.com>, Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, Christian Borntraeger <borntraeger@...ibm.com>, Russell King <linux@...linux.org.uk>, Will Deacon <will.deacon@....com>, Catalin Marinas <catalin.marinas@....com>, Mark Rutland <mark.rutland@....com>, James Morse <james.morse@....com>, linux-s390 <linux-s390@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Linux API <linux-api@...r.kernel.org>, the arch/x86 maintainers <x86@...nel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Al Viro <viro@...iv.linux.org.uk> Subject: Re: Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode * Kees Cook <keescook@...omium.org> wrote: > > There's the option of using GCC plugins now that the infrastructure was > > upstreamed from grsecurity. It can be used as part of the regular build > > process and as long as the analysis is pretty simple it shouldn't hurt compile > > time much. > > Well, and that the situation may arise due to memory corruption, not from > poorly-matched set_fs() calls, which static analysis won't help solve. We need > to catch this bad kernel state because it is a very bad state to run in. If memory corruption corrupted the task state into having addr_limit set to KERNEL_DS then there's already a fair chance that it's game over: it could also have set *uid to 0, or changed a sensitive PF_ flag, or a number of other things... Furthermore, think about it: there's literally an infinite amount of corrupted task states that could be a security problem and that could be checked after every system call. Do we want to check every one of them? Thanks, Ingo
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