netdev - Re: [PATCH net] bpf: fix regression on verifier pruning wrt map lookups

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Message-Id: <20161217.105157.1777770626254774920.davem@davemloft.net>
Date:   Sat, 17 Dec 2016 10:51:57 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     daniel@...earbox.net
Cc:     ast@...com, jbacik@...com, tgraf@...g.ch, netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: fix regression on verifier pruning wrt map
 lookups

From: Daniel Borkmann <daniel@...earbox.net>
Date: Thu, 15 Dec 2016 01:30:06 +0100

> Commit 57a09bf0a416 ("bpf: Detect identical PTR_TO_MAP_VALUE_OR_NULL
> registers") introduced a regression where existing programs stopped
> loading due to reaching the verifier's maximum complexity limit,
> whereas prior to this commit they were loading just fine; the affected
> program has roughly 2k instructions.
> 
> What was found is that state pruning couldn't be performed effectively
> anymore due to mismatches of the verifier's register state, in particular
> in the id tracking. It doesn't mean that 57a09bf0a416 is incorrect per
> se, but rather that verifier needs to perform a lot more work for the
> same program with regards to involved map lookups.
 ...
> Fixes: 57a09bf0a416 ("bpf: Detect identical PTR_TO_MAP_VALUE_OR_NULL registers")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Acked-by: Thomas Graf <tgraf@...g.ch>
> Acked-by: Alexei Starovoitov <ast@...nel.org>

Applied.