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 v2] ipv6: fix data race in fib6_metric_set() using cmpxchg
Date: Mon, 30 Mar 2026 17:46:28 -0700 [thread overview]
Message-ID: <20260330174628.0cb1ebc6@kernel.org> (raw)
In-Reply-To: <20260327-b4-fib6_metric_set-kmemleak-v2-1-366b2c78b5c2@gmail.com>
On Fri, 27 Mar 2026 10:24:47 +0800 Hangbin Liu wrote:
> --- a/net/ipv6/ip6_fib.c
> +++ b/net/ipv6/ip6_fib.c
> @@ -730,17 +730,24 @@ void fib6_metric_set(struct fib6_info *f6i, int metric, u32 val)
> if (!f6i)
> return;
>
> - 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;
Why does this exist? To cast away the const?
> struct dst_metrics *p = kzalloc_obj(*p, GFP_ATOMIC);
>
> if (!p)
> return;
>
> + p->metrics[metric - 1] = val;
> refcount_set(&p->refcnt, 1);
> - f6i->fib6_metrics = p;
> + if (cmpxchg(&f6i->fib6_metrics, dflt, p) != dflt)
> + kfree(p);
> + else
> + return;
> }
>
> - f6i->fib6_metrics->metrics[metric - 1] = val;
> + struct dst_metrics *m = READ_ONCE(f6i->fib6_metrics);
No variable declarations in the middle of a function please.
> + WRITE_ONCE(m->metrics[metric - 1], val);
> }
next prev parent reply other threads:[~2026-03-31 0:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-27 2:24 [PATCH net v2] ipv6: fix data race in fib6_metric_set() using cmpxchg Hangbin Liu
2026-03-28 11:22 ` Jiayuan Chen
2026-03-31 1:34 ` Hangbin Liu
2026-03-31 0:46 ` Jakub Kicinski [this message]
2026-03-31 1:12 ` Hangbin Liu
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