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Date: Wed, 1 Apr 2026 17:47:16 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Hangbin Liu <liuhangbin@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>, David Ahern
 <dsahern@kernel.org>, Eric Dumazet <edumazet@google.com>, Paolo Abeni
 <pabeni@redhat.com>, Simon Horman <horms@kernel.org>, Jiayuan Chen
 <jiayuan.chen@linux.dev>, David Ahern <dsahern@gmail.com>,
 netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Fei Liu
 <feliu@redhat.com>
Subject: Re: [PATCH net v3] ipv6: fix data race in fib6_metric_set() using
 cmpxchg
Message-ID: <20260401174716.6b9fd993@kernel.org>
In-Reply-To: <20260331-b4-fib6_metric_set-kmemleak-v3-1-88d27f4d8825@gmail.com>
References: <20260331-b4-fib6_metric_set-kmemleak-v3-1-88d27f4d8825@gmail.com>
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On Tue, 31 Mar 2026 12:17:18 +0800 Hangbin Liu wrote:
> -	if (f6i->fib6_metrics == &dst_default_metrics) {
> +	if (READ_ONCE(f6i->fib6_metrics) == &dst_default_metrics) {
> +		struct dst_metrics *dflt = (struct dst_metrics *)&dst_default_metrics;
>  		struct dst_metrics *p = kzalloc_obj(*p, GFP_ATOMIC);

Orthogonal, but I forgot to reply - could you poke at making
cmpxchg() take const on the second argument? The type of the
first and third args must obviously match exactly but the
second one is just a reference, it should be okay to make
it const :/