From: Kuniyuki Iwashima <kuniyu@google.com>
To: yuyanghuang@google.com
Cc: davem@davemloft.net, dsahern@kernel.org, edumazet@google.com,
horms@kernel.org, idosch@nvidia.com, kuba@kernel.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
pabeni@redhat.com, stable@vger.kernel.org,
xiyou.wangcong@gmail.com, Kuniyuki Iwashima <kuniyu@google.com>
Subject: Re: [PATCH net v3] ipv4: igmp: remove multicast group from hash table on device destruction
Date: Thu, 2 Jul 2026 05:49:42 +0000 [thread overview]
Message-ID: <20260702054952.639157-1-kuniyu@google.com> (raw)
In-Reply-To: <20260701235014.73505-1-yuyanghuang@google.com>
From: Yuyang Huang <yuyanghuang@google.com>
Date: Thu, 2 Jul 2026 08:50:14 +0900
> 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.
>
> BUG: KASAN: slab-use-after-free in ip_check_mc_rcu+0x149/0x3f0
> Read of size 4 at addr ffff888009bf1408 by task mausezahn/2276
>
> Call Trace:
> <IRQ>
> dump_stack_lvl+0x67/0x90
> print_report+0x175/0x7c0
> kasan_report+0x147/0x180
> ip_check_mc_rcu+0x149/0x3f0
> udp_v4_early_demux+0x36d/0x12d0
> ip_rcv_finish_core+0xb8b/0x1390
> ip_rcv_finish+0x54/0x120
> NF_HOOK+0x213/0x2b0
> __netif_receive_skb+0x126/0x340
> process_backlog+0x4f2/0xf00
> __napi_poll+0x92/0x2c0
> net_rx_action+0x583/0xc60
> handle_softirqs+0x236/0x7f0
> do_softirq+0x57/0x80
> </IRQ>
>
> Allocated by task 2239:
> kasan_save_track+0x3e/0x80
> __kasan_kmalloc+0x72/0x90
> ____ip_mc_inc_group+0x31a/0xa40
> __ip_mc_join_group+0x334/0x3f0
> do_ip_setsockopt+0x16fa/0x2010
> ip_setsockopt+0x3f/0x90
> do_sock_setsockopt+0x1ad/0x300
>
> Freed by task 0:
> kasan_save_track+0x3e/0x80
> kasan_save_free_info+0x40/0x50
> __kasan_slab_free+0x3a/0x60
> __rcu_free_sheaf_prepare+0xd4/0x220
> rcu_free_sheaf+0x36/0x190
> rcu_core+0x8d9/0x12f0
> handle_softirqs+0x236/0x7f0
>
> 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: Kuniyuki Iwashima <kuniyu@google.com>
next prev parent reply other threads:[~2026-07-02 5:49 UTC|newest]
Thread overview: 3+ 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 [this message]
2026-07-02 7:05 ` Ido Schimmel
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