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
| ||
|
Date: Tue, 10 Mar 2020 16:02:48 -0500 From: ebiederm@...ssion.com (Eric W. Biederman) To: Kees Cook <keescook@...omium.org> Cc: Bernd Edlinger <bernd.edlinger@...mail.de>, Christian Brauner <christian.brauner@...ntu.com>, Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>, Alexander Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Alexey Dobriyan <adobriyan@...il.com>, Thomas Gleixner <tglx@...utronix.de>, Oleg Nesterov <oleg@...hat.com>, Frederic Weisbecker <frederic@...nel.org>, Andrei Vagin <avagin@...il.com>, Ingo Molnar <mingo@...nel.org>, "Peter Zijlstra \(Intel\)" <peterz@...radead.org>, Yuyang Du <duyuyang@...il.com>, David Hildenbrand <david@...hat.com>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Anshuman Khandual <anshuman.khandual@....com>, David Howells <dhowells@...hat.com>, James Morris <jamorris@...ux.microsoft.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Shakeel Butt <shakeelb@...gle.com>, Jason Gunthorpe <jgg@...pe.ca>, Christian Kellner <christian@...lner.me>, Andrea Arcangeli <aarcange@...hat.com>, Aleksa Sarai <cyphar@...har.com>, "Dmitry V. Levin" <ldv@...linux.org>, "linux-doc\@vger.kernel.org" <linux-doc@...r.kernel.org>, "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>, "linux-fsdevel\@vger.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-mm\@kvack.org" <linux-mm@...ck.org>, "stable\@vger.kernel.org" <stable@...r.kernel.org>, "linux-api\@vger.kernel.org" <linux-api@...r.kernel.org> Subject: Re: [PATCH v2 5/5] exec: Add a exec_update_mutex to replace cred_guard_mutex Kees Cook <keescook@...omium.org> writes: > On Mon, Mar 09, 2020 at 02:02:37PM -0500, Eric W. Biederman wrote: >> exec: Add exec_update_mutex to replace cred_guard_mutex >> >> The cred_guard_mutex is problematic as it is held over possibly >> indefinite waits for userspace. The possilbe indefinite waits for >> userspace that I have identified are: The cred_guard_mutex is held in >> PTRACE_EVENT_EXIT waiting for the tracer. The cred_guard_mutex is >> held over "put_user(0, tsk->clear_child_tid)" in exit_mm(). The >> cred_guard_mutex is held over "get_user(futex_offset, ...") in >> exit_robust_list. The cred_guard_mutex held over copy_strings. > > I suspect you're not trying to make a comprehensive list here, but do > you want to mention seccomp too (since it's yet another weird case). I was calling out all of the places I have found so far where cred_guard_mutex is held over waiting for userspace to maybe do something. Those places are what cause our deadlocks. >> [...] >> Holding a mutex over any of those possibly indefinite waits for >> userspace does not appear necessary. Add exec_update_mutex that will >> just cover updating the process during exec where the permissions and >> the objects pointed to by the task struct may be out of sync. > > Should the specific resources be pointed out here? creds, mm, ... ? > > But otherwise, yup, looks sane: Probably not. The design is if exec changes it we will hold the cred_guard_mutex over it, so things are semi-atomic. > Reviewed-by: Kees Cook <keescook@...omium.org> Eric
Powered by blists - more mailing lists