netdev - Re: [PATCH net 8/8] ipv6: mcast: extend RCU protection in igmp6

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Message-ID: <20250210030746.57432-1-kuniyu@amazon.com>
Date: Mon, 10 Feb 2025 12:07:46 +0900
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <edumazet@...gle.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <eric.dumazet@...il.com>,
	<horms@...nel.org>, <kuba@...nel.org>, <kuniyu@...zon.com>,
	<netdev@...r.kernel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH net 8/8] ipv6: mcast: extend RCU protection in igmp6_send()

From: Eric Dumazet <edumazet@...gle.com>
Date: Fri,  7 Feb 2025 13:58:40 +0000
> igmp6_send() can be called without RTNL or RCU being held.
> 
> Extend RCU protection so that we can safely fetch the net pointer
> and avoid a potential UAF.
> 
> Note that we no longer can use sock_alloc_send_skb() because
> ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep.
> 
> Instead use alloc_skb() and charge the net->ipv6.igmp_sk
> socket under RCU protection.
> 
> Fixes: b8ad0cbc58f7 ("[NETNS][IPV6] mcast - handle several network namespace")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>