netdev - Re: [PATCH] Revert "batman-adv: prefer kfree_rcu() over call

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]

Date: Wed, 12 Jun 2024 20:22:49 +0200
From: Sven Eckelmann <sven@...fation.org>
To: "Paul E. McKenney" <paulmck@...nel.org>, b.a.t.m.a.n@...ts.open-mesh.org
Cc: b.a.t.m.a.n@...ts.open-mesh.org, Dmitry Antipov <dmantipov@...dex.ru>,
 netdev@...r.kernel.org, rcu@...r.kernel.org,
 Linus Lüssing <linus.luessing@...3.blue>
Subject:
 Re: [PATCH] Revert "batman-adv: prefer kfree_rcu() over call_rcu() with
 free-only callbacks"

On Wednesday, 12 June 2024 18:31:57 CEST Linus Lüssing wrote:
> On Wed, Jun 12, 2024 at 09:06:25AM -0700, Paul E. McKenney wrote:
> > We are looking into nice ways of solving this, but in the meantime,
> > yes, if you are RCU-freeing slab objects into a slab that is destroyed
> > at module-unload time, you currently need to stick with call_rcu()
> > and rcu_barrier().
> >
> > We do have some potential solutions to allow use of kfree_rcu() with
> > this sort of slab, but they are still strictly potential.
> >
> > Apologies for my having failed to foresee this particular trap!
> 
> No worries, thanks for the help and clarification! This at least
> restored my sanity, was starting to doubt my understanding of RCU
> and the batman-adv code the longer I tried to find the issue in
> batman-adv :D.

Thanks Linus and Paul. I've queued up the revert. But feel free to submit a 
version with updated text in case you want to incorporate information from 
this thread.

Kind regards,
	Sven
Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)