From: Ido Schimmel <idosch@nvidia.com>
To: Yuyang Huang <yuyanghuang@google.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Cong Wang <xiyou.wangcong@gmail.com>,
David Ahern <dsahern@kernel.org>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH net v3] ipv4: igmp: remove multicast group from hash table on device destruction
Date: Thu, 2 Jul 2026 10:05:03 +0300 [thread overview]
Message-ID: <20260702070503.GA1544468@shredder> (raw)
In-Reply-To: <20260701235014.73505-1-yuyanghuang@google.com>
On Thu, Jul 02, 2026 at 08:50:14AM +0900, Yuyang Huang wrote:
> When a device is destroyed under RTNL, ip_mc_destroy_dev() iterates through
> the multicast list and calls ip_ma_put() on each membership, scheduling
> them for RCU reclamation. However, they are not unlinked from the device's
> multicast hash table (mc_hash).
>
> Since the device remains published in dev->ip_ptr until after
> ip_mc_destroy_dev() completes, concurrent RCU readers traversing mc_hash
> can still locate and access the multicast group after its refcount is
> decremented. If the RCU callback runs and frees the group while a reader is
> accessing it, a use-after-free occurs.
>
> Fix this by unlinking the multicast group from mc_hash using
> ip_mc_hash_remove() before scheduling it for reclamation.
[...]
>
> Fixes: e9897071350b ("igmp: hash a hash table to speedup ip_check_mc_rcu()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Yuyang Huang <yuyanghuang@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
next prev parent reply other threads:[~2026-07-02 7:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 23:50 [PATCH net v3] ipv4: igmp: remove multicast group from hash table on device destruction Yuyang Huang
2026-07-02 5:49 ` Kuniyuki Iwashima
2026-07-02 7:05 ` Ido Schimmel [this message]
2026-07-07 10:20 ` patchwork-bot+netdevbpf
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