linux-kernel - Re: [PATCH] rhashtable: Fix potential deadlock by moving schedule

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] [day] [month] [year] [list]

Message-ID: <Z0lVftsFRSSkPkld@gondor.apana.org.au>
Date: Fri, 29 Nov 2024 13:47:42 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Breno Leitao <leitao@...ian.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Thomas Graf <tgraf@...g.ch>,
	Tejun Heo <tj@...nel.org>, Hao Luo <haoluo@...gle.com>,
	Josh Don <joshdon@...gle.com>, Barret Rhoden <brho@...gle.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rhashtable: Fix potential deadlock by moving
 schedule_work outside lock

On Thu, Nov 28, 2024 at 04:16:25AM -0800, Breno Leitao wrote:
> Move the hash table growth check and work scheduling outside the
> rht lock to prevent a possible circular locking dependency.
> 
> The original implementation could trigger a lockdep warning due to
> a potential deadlock scenario involving nested locks between
> rhashtable bucket, rq lock, and dsq lock. By relocating the
> growth check and work scheduling after releasing the rth lock, we break
> this potential deadlock chain.
> 
> This change expands the flexibility of rhashtable by removing
> restrictive locking that previously limited its use in scheduler
> and workqueue contexts.

Could you please explain the deadlock? Is the workqueue system actually
using rhashtable?

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt