linux-kernel - Re: [PATCH v2 0/5] implement lightweight guard pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241023062417.3862170-1-dvyukov@google.com>
Date: Wed, 23 Oct 2024 08:24:17 +0200
From: Dmitry Vyukov <dvyukov@...gle.com>
To: fw@...eb.enyo.de
Cc: James.Bottomley@...senPartnership.com, Liam.Howlett@...cle.com, 
	akpm@...ux-foundation.org, arnd@...db.de, brauner@...nel.org, 
	chris@...kel.net, david@...hat.com, deller@....de, hch@...radead.org, 
	ink@...assic.park.msu.ru, jannh@...gle.com, jcmvbkbc@...il.com, 
	jeffxu@...omium.org, jhubbard@...dia.com, linux-alpha@...r.kernel.org, 
	linux-api@...r.kernel.org, linux-arch@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-mips@...r.kernel.org, linux-mm@...ck.org, linux-parisc@...r.kernel.org, 
	lorenzo.stoakes@...cle.com, mattst88@...il.com, muchun.song@...ux.dev, 
	paulmck@...nel.org, richard.henderson@...aro.org, shuah@...nel.org, 
	sidhartha.kumar@...cle.com, surenb@...gle.com, tsbogend@...ha.franken.de, 
	vbabka@...e.cz, willy@...radead.org, elver@...gle.com
Subject: Re: [PATCH v2 0/5] implement lightweight guard pages

Hi Florian, Lorenzo,

This looks great!

What I am VERY interested in is if poisoned pages cause SIGSEGV even when
the access happens in the kernel. Namely, the syscall still returns EFAULT,
but also SIGSEGV is queued on return to user-space.

Catching bad accesses in system calls is currently the weak spot for
all user-space bug detection tools (GWP-ASan, libefence, libefency, etc).
It's almost possible with userfaultfd, but catching faults in the kernel
requires admin capability, so not really an option for generic bug
detection tools (+inconvinience of userfaultfd setup/handler).
Intercepting all EFAULT from syscalls is not generally possible
(w/o ptrace, usually not an option as well), and EFAULT does not always
mean a bug.

Triggering SIGSEGV even in syscalls would be not just a performance
optimization, but a new useful capability that would allow it to catch
more bugs.

Thanks