From: Ido Schimmel <idosch@nvidia.com>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
David Ahern <dsahern@kernel.org>, Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org, eric.dumazet@gmail.com,
Taehee Yoo <ap420073@gmail.com>
Subject: Re: [PATCH v2 net 1/5] ipv6: mcast: fix RCU list diversion in ip6_mc_del1_src()
Date: Sun, 30 Aug 2026 18:44:06 +0300 [thread overview]
Message-ID: <20260830154406.GA2974032@shredder> (raw)
In-Reply-To: <20260828084531.1826790-2-edumazet@google.com>
On Fri, Aug 28, 2026 at 08:45:27AM +0000, Eric Dumazet wrote:
> When removing a source filter whose count reaches zero, ip6_mc_del1_src()
> unlinks psf from pmc->mca_sources. If the filter was previously active,
> the code moved psf directly into pmc->mca_tomb by updating psf->sf_next.
>
> Because pmc->mca_sources is traversed locklessly under RCU (e.g. by
> ipv6_chk_mcast_addr()), mutating psf->sf_next before a grace period
> elapses diverts concurrent readers to the tombstone list. Consequently,
> readers miss remaining active sources in pmc->mca_sources and improperly
> examine deleted tombstone entries.
>
> Fix this by allocating a new tombstone node for pmc->mca_tomb (as done
> in sf_setstate()) and retiring the original psf via kfree_rcu().
>
> Fixes: 4b200e398953 ("mld: convert ip6_sf_list to RCU")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Taehee Yoo <ap420073@gmail.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
next prev parent reply other threads:[~2026-08-30 15:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-28 8:45 [PATCH v2 net 0/5] ipv6: mcast: RCU and timer fixes Eric Dumazet
2026-08-28 8:45 ` [PATCH v2 net 1/5] ipv6: mcast: fix RCU list diversion in ip6_mc_del1_src() Eric Dumazet
2026-08-30 15:44 ` Ido Schimmel [this message]
2026-08-28 8:45 ` [PATCH v2 net 2/5] ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source() Eric Dumazet
2026-08-30 15:44 ` Ido Schimmel
2026-08-28 8:45 ` [PATCH v2 net 3/5] ipv6: mcast: fix delay calculation in igmp6_join_group() Eric Dumazet
2026-08-30 15:44 ` Ido Schimmel
2026-08-28 8:45 ` [PATCH v2 net 4/5] ipv6: mcast: use rcu_assign_pointer() for __rcu list updates Eric Dumazet
2026-08-30 15:45 ` Ido Schimmel
2026-08-28 8:45 ` [PATCH v2 net 5/5] ipv6: mcast: use jiffies_delta_to_clock_t() in igmp6_mc_seq_show() Eric Dumazet
2026-08-30 15:45 ` Ido Schimmel
2026-09-01 1:10 ` [PATCH v2 net 0/5] ipv6: mcast: RCU and timer fixes patchwork-bot+netdevbpf
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