netdev - Re: [PATCH net] net: read sk->sk_family once in sk_mc

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Message-ID: <20230828191450.57704-1-kuniyu@amazon.com>
Date: Mon, 28 Aug 2023 12:14:50 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <edumazet@...gle.com>
CC: <davem@...emloft.net>, <eric.dumazet@...il.com>, <kuba@...nel.org>,
	<netdev@...r.kernel.org>, <pabeni@...hat.com>, <syzkaller@...glegroups.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>
Subject: Re: [PATCH net] net: read sk->sk_family once in sk_mc_loop()

From: Eric Dumazet <edumazet@...gle.com>
Date: Mon, 28 Aug 2023 11:30:55 +0000
> syzbot is playing with IPV6_ADDRFORM quite a lot these days,
> and managed to hit the WARN_ON_ONCE(1) in sk_mc_loop()
> 
> We have many more similar issues to fix.
> 
> WARNING: CPU: 1 PID: 1593 at net/core/sock.c:782 sk_mc_loop+0x165/0x260
> Modules linked in:
> CPU: 1 PID: 1593 Comm: kworker/1:3 Not tainted 6.1.40-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
> Workqueue: events_power_efficient gc_worker
> RIP: 0010:sk_mc_loop+0x165/0x260 net/core/sock.c:782
> Code: 34 1b fd 49 81 c7 18 05 00 00 4c 89 f8 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 ff e8 25 36 6d fd 4d 8b 37 eb 13 e8 db 33 1b fd <0f> 0b b3 01 eb 34 e8 d0 33 1b fd 45 31 f6 49 83 c6 38 4c 89 f0 48
> RSP: 0018:ffffc90000388530 EFLAGS: 00010246
> RAX: ffffffff846d9b55 RBX: 0000000000000011 RCX: ffff88814f884980
> RDX: 0000000000000102 RSI: ffffffff87ae5160 RDI: 0000000000000011
> RBP: ffffc90000388550 R08: 0000000000000003 R09: ffffffff846d9a65
> R10: 0000000000000002 R11: ffff88814f884980 R12: dffffc0000000000
> R13: ffff88810dbee000 R14: 0000000000000010 R15: ffff888150084000
> FS: 0000000000000000(0000) GS:ffff8881f6b00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000180 CR3: 000000014ee5b000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <IRQ>
> [<ffffffff8507734f>] ip6_finish_output2+0x33f/0x1ae0 net/ipv6/ip6_output.c:83
> [<ffffffff85062766>] __ip6_finish_output net/ipv6/ip6_output.c:200 [inline]
> [<ffffffff85062766>] ip6_finish_output+0x6c6/0xb10 net/ipv6/ip6_output.c:211
> [<ffffffff85061f8c>] NF_HOOK_COND include/linux/netfilter.h:298 [inline]
> [<ffffffff85061f8c>] ip6_output+0x2bc/0x3d0 net/ipv6/ip6_output.c:232
> [<ffffffff852071cf>] dst_output include/net/dst.h:444 [inline]
> [<ffffffff852071cf>] ip6_local_out+0x10f/0x140 net/ipv6/output_core.c:161
> [<ffffffff83618fb4>] ipvlan_process_v6_outbound drivers/net/ipvlan/ipvlan_core.c:483 [inline]
> [<ffffffff83618fb4>] ipvlan_process_outbound drivers/net/ipvlan/ipvlan_core.c:529 [inline]
> [<ffffffff83618fb4>] ipvlan_xmit_mode_l3 drivers/net/ipvlan/ipvlan_core.c:602 [inline]
> [<ffffffff83618fb4>] ipvlan_queue_xmit+0x1174/0x1be0 drivers/net/ipvlan/ipvlan_core.c:677
> [<ffffffff8361ddd9>] ipvlan_start_xmit+0x49/0x100 drivers/net/ipvlan/ipvlan_main.c:229
> [<ffffffff84763fc0>] netdev_start_xmit include/linux/netdevice.h:4925 [inline]
> [<ffffffff84763fc0>] xmit_one net/core/dev.c:3644 [inline]
> [<ffffffff84763fc0>] dev_hard_start_xmit+0x320/0x980 net/core/dev.c:3660
> [<ffffffff8494c650>] sch_direct_xmit+0x2a0/0x9c0 net/sched/sch_generic.c:342
> [<ffffffff8494d883>] qdisc_restart net/sched/sch_generic.c:407 [inline]
> [<ffffffff8494d883>] __qdisc_run+0xb13/0x1e70 net/sched/sch_generic.c:415
> [<ffffffff8478c426>] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125
> [<ffffffff84796eac>] net_tx_action+0x7ac/0x940 net/core/dev.c:5247
> [<ffffffff858002bd>] __do_softirq+0x2bd/0x9bd kernel/softirq.c:599
> [<ffffffff814c3fe8>] invoke_softirq kernel/softirq.c:430 [inline]
> [<ffffffff814c3fe8>] __irq_exit_rcu+0xc8/0x170 kernel/softirq.c:683
> [<ffffffff814c3f09>] irq_exit_rcu+0x9/0x20 kernel/softirq.c:695
> 
> Fixes: 7ad6848c7e81 ("ip: fix mc_loop checks for tunnels with multicast outer addresses")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

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


> ---
>  net/core/sock.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index c9cffb7acbeae02c656a00760bda09090014abef..160ca1df6140a2b653895f13167e7064b94ccdb3 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -765,7 +765,8 @@ bool sk_mc_loop(struct sock *sk)
>  		return false;
>  	if (!sk)
>  		return true;
> -	switch (sk->sk_family) {
> +	/* IPV6_ADDRFORM can change sk->sk_family under us. */
> +	switch (READ_ONCE(sk->sk_family)) {
>  	case AF_INET:
>  		return inet_sk(sk)->mc_loop;
>  #if IS_ENABLED(CONFIG_IPV6)
> -- 
> 2.42.0.rc1.204.g551eb34607-goog