linux-kernel - Re: [PATCH RESEND] locking/ww_mutex: Adjust to lockdep nest

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: <20241004101601.GQ18071@noisy.programming.kicks-ass.net>
Date: Fri, 4 Oct 2024 12:16:01 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
Cc: intel-xe@...ts.freedesktop.org, Ingo Molnar <mingo@...hat.com>,
	Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Maarten Lankhorst <maarten@...khorst.se>,
	Christian König <christian.koenig@....com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] locking/ww_mutex: Adjust to lockdep nest_lock
 requirements

On Wed, Oct 02, 2024 at 02:56:11PM +0200, Thomas Hellström wrote:
> When using mutex_acquire_nest() with a nest_lock, lockdep refcounts the
> number of acquired lockdep_maps of mutexes of the same class, and also
> keeps a pointer to the first acquired lockdep_map of a class. That pointer
> is then used for various comparison-, printing- and checking purposes,
> but there is no mechanism to actively ensure that lockdep_map stays in
> memory. Instead, a warning is printed if the lockdep_map is freed and
> there are still held locks of the same lock class, even if the lockdep_map
> itself has been released.
> 
> In the context of WW/WD transactions that means that if a user unlocks
> and frees a ww_mutex from within an ongoing ww transaction, and that
> mutex happens to be the first ww_mutex grabbed in the transaction,
> such a warning is printed and there might be a risk of a UAF.

I'm assuming you actually hit this?

Anyway, work around seems sane enough, thanks!