From: Florian Westphal <fw@strlen.de>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Florian Westphal <fw@strlen.de>, Phil Sutter <phil@nwl.cc>,
netfilter-devel@vger.kernel.org
Subject: Re: [nf PATCH 2/5] netfilter: nf_tables: Add locking for NFT_MSG_GETRULE_RESET requests
Date: Mon, 25 Sep 2023 21:53:17 +0200 [thread overview]
Message-ID: <20230925195317.GC22532@breakpoint.cc> (raw)
In-Reply-To: <ZRFTx6pFYt2tZuSy@calendula>
Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> On Sat, Sep 23, 2023 at 06:18:13PM +0200, Florian Westphal wrote:
> > callback_that_might_reset()
> > {
> > try_module_get ...
> > rcu_read_unlock()
> > mutex_lock(net->commit_mutex)
> > dumper();
> > mutex_unlock(net->commit_mutex)
> > rcu_read_lock();
> > module_put()
> > }
> >
> > should do the trick.
>
> Idiom above LGTM, *except for net->commit_mutex*. Please do not use
> ->commit_mutex: This will stall ruleset updates for no reason, netlink
> dump would grab and release such mutex for each netlink_recvmsg() call
> and netlink dump side will always retry because of NLM_F_EINTR.
It will stall updates, but for good reason: we are making changes to the
expressions state.
We even emit AUDIT messages about this.
So, I think the commit mutex is appropirate here.
That said, if you totally disagree, then I suppose a new "reset" mutex
could be used instead.
next prev parent reply other threads:[~2023-09-25 19:53 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-23 1:38 [nf PATCH 0/5] Introduce locking for reset requests Phil Sutter
2023-09-23 1:38 ` [nf PATCH 1/5] netfilter: nf_tables: Don't allocate nft_rule_dump_ctx Phil Sutter
2023-09-23 1:38 ` [nf PATCH 2/5] netfilter: nf_tables: Add locking for NFT_MSG_GETRULE_RESET requests Phil Sutter
2023-09-23 11:04 ` Florian Westphal
2023-09-23 15:03 ` Phil Sutter
2023-09-23 16:18 ` Florian Westphal
2023-09-25 9:32 ` Pablo Neira Ayuso
2023-09-25 19:53 ` Florian Westphal [this message]
2023-09-26 9:34 ` Phil Sutter
2023-09-26 10:09 ` Pablo Neira Ayuso
2023-09-26 12:14 ` Phil Sutter
2023-09-26 13:34 ` Pablo Neira Ayuso
2023-09-26 13:59 ` Phil Sutter
2023-09-27 11:41 ` Florian Westphal
2023-09-27 12:54 ` Phil Sutter
2023-09-25 11:02 ` Pablo Neira Ayuso
2023-09-25 10:47 ` Pablo Neira Ayuso
2023-09-26 9:14 ` Phil Sutter
2023-09-26 10:00 ` Pablo Neira Ayuso
2023-09-25 10:48 ` Pablo Neira Ayuso
2023-09-25 11:01 ` Pablo Neira Ayuso
2023-09-23 1:38 ` [nf PATCH 3/5] netfilter: nf_tables: Introduce struct nft_obj_dump_ctx Phil Sutter
2023-09-23 1:38 ` [nf PATCH 4/5] netfilter: nf_tables: Add locking for NFT_MSG_GETOBJ_RESET requests Phil Sutter
2023-09-23 1:38 ` [nf PATCH 5/5] netfilter: nf_tables: Add locking for NFT_MSG_GETSETELEM_RESET requests Phil Sutter
2023-09-25 10:53 ` Pablo Neira Ayuso
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