linux-kernel - Re: [PATCH net] netpoll: guard __netpoll_send

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: <580ce055-b710-4e97-8d91-1cfea7ec4881@lunn.ch>
Date: Wed, 5 Mar 2025 17:09:14 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Breno Leitao <leitao@...ian.org>
Cc: Jakub Kicinski <kuba@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Amerigo Wang <amwang@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...a.com
Subject: Re: [PATCH net] netpoll: guard __netpoll_send_skb() with RCU read
 lock

On Wed, Mar 05, 2025 at 01:09:49AM -0800, Breno Leitao wrote:
> Hello Jakub,
> 
> On Tue, Mar 04, 2025 at 05:47:32PM -0800, Jakub Kicinski wrote:
> > On Mon, 03 Mar 2025 03:44:12 -0800 Breno Leitao wrote:
> > > +	guard(rcu)();
> > 
> > Scoped guards if you have to.
> > Preferably just lock/unlock like a normal person..
> 
> Sure, I thought that we would be moving to scoped guards all across the
> board, at least that was my reading for a similar patch I sent a while
> ago:
> 
> 	https://lore.kernel.org/all/20250224123016.GA17456@noisy.programming.kicks-ass.net/
> 
> Anyway, in which case should I use scoped guard instead of just being
> like a normal person?

https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html

  Section 1.6.5: Using device-managed and cleanup.h constructs

  Netdev remains skeptical about promises of all “auto-cleanup” APIs,
  including even devm_ helpers, historically. They are not the
  preferred style of implementation, merely an acceptable one.

  Use of guard() is discouraged within any function longer than 20
  lines, scoped_guard() is considered more readable. Using normal
  lock/unlock is still (weakly) preferred.

  Low level cleanup constructs (such as __free()) can be used when
  building APIs and helpers, especially scoped iterators. However,
  direct use of __free() within networking core and drivers is
  discouraged. Similar guidance applies to declaring variables
  mid-function.

So you need to spend time to find out what each subsystems view is on
various APIs.

	Andrew