netdev - Re: [PATCH net-next] mptcp: fix possible NULL dereferences

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Date: Mon, 06 May 2024 16:29:24 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
 <davem@...emloft.net>,  Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, syzbot
 <syzkaller@...glegroups.com>, Jason Xing <kernelxing@...cent.com>, Matthieu
 Baerts <matttbe@...nel.org>
Subject: Re: [PATCH net-next] mptcp: fix possible NULL dereferences

On Mon, 2024-05-06 at 12:30 +0000, Eric Dumazet wrote:
> subflow_add_reset_reason(skb, ...) can fail.

whooops... yes, indeed. 

> We can not assume mptcp_get_ext(skb) always return a non NULL pointer.
> 
> syzbot reported:
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
> CPU: 0 PID: 5098 Comm: syz-executor132 Not tainted 6.9.0-rc6-syzkaller-01478-gcdc74c9d06e7 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
>  RIP: 0010:subflow_v6_route_req+0x2c7/0x490 net/mptcp/subflow.c:388
> Code: 8d 7b 07 48 89 f8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 c0 01 00 00 0f b6 43 07 48 8d 1c c3 48 83 c3 18 48 89 d8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 84 01 00 00 0f b6 5b 01 83 e3 0f 48 89
> RSP: 0018:ffffc9000362eb68 EFLAGS: 00010206
> RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff888022039e00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff88807d961140 R08: ffffffff8b6cb76b R09: 1ffff1100fb2c230
> R10: dffffc0000000000 R11: ffffed100fb2c231 R12: dffffc0000000000
> R13: ffff888022bfe273 R14: ffff88802cf9cc80 R15: ffff88802ad5a700
> FS:  0000555587ad2380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f420c3f9720 CR3: 0000000022bfc000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>   tcp_conn_request+0xf07/0x32c0 net/ipv4/tcp_input.c:7180
>   tcp_rcv_state_process+0x183c/0x4500 net/ipv4/tcp_input.c:6663
>   tcp_v6_do_rcv+0x8b2/0x1310 net/ipv6/tcp_ipv6.c:1673
>   tcp_v6_rcv+0x22b4/0x30b0 net/ipv6/tcp_ipv6.c:1910
>   ip6_protocol_deliver_rcu+0xc76/0x1570 net/ipv6/ip6_input.c:438
>   ip6_input_finish+0x186/0x2d0 net/ipv6/ip6_input.c:483
>   NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
>   NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
>   __netif_receive_skb_one_core net/core/dev.c:5625 [inline]
>   __netif_receive_skb+0x1ea/0x650 net/core/dev.c:5739
>   netif_receive_skb_internal net/core/dev.c:5825 [inline]
>   netif_receive_skb+0x1e8/0x890 net/core/dev.c:5885
>   tun_rx_batched+0x1b7/0x8f0 drivers/net/tun.c:1549
>   tun_get_user+0x2f35/0x4560 drivers/net/tun.c:2002
>   tun_chr_write_iter+0x113/0x1f0 drivers/net/tun.c:2048
>   call_write_iter include/linux/fs.h:2110 [inline]
>   new_sync_write fs/read_write.c:497 [inline]
>   vfs_write+0xa84/0xcb0 fs/read_write.c:590
>   ksys_write+0x1a0/0x2c0 fs/read_write.c:643
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Fixes: 3e140491dd80 ("mptcp: support rstreason for passive reset")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Jason Xing <kernelxing@...cent.com>
> Cc: Matthieu Baerts (NGI0) <matttbe@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>

LGTM, thanks!

Acked-by: Paolo Abeni <pabeni@...hat.com>