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Date:   Mon, 5 Jun 2023 23:42:06 +0300
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In-Reply-To: <20230413-b4-vsock-dgram-v3-0-c2414413ef6a@bytedance.com>
To:     Bobby Eshleman <bobby.eshleman@bytedance.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Bryan Tan <bryantan@vmware.com>
CC:     <kvm@vger.kernel.org>, <virtualization@lists.linux-foundation.org>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-hyperv@vger.kernel.org>,
        Bobby Eshleman <bobby.eshleman@bytedance.com>,
        Jiang Wang <jiang.wang@bytedance.com>
From:   Arseniy Krasnov <avkrasnov@sberdevices.ru>
Subject: Re: [PATCH RFC net-next v3 0/8] virtio/vsock: support datagrams
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Hello Bobby!

Thanks for this patchset, really interesting!

I applied it on head:

https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=d20dd0ea14072e8a90ff864b2c1603bd68920b4b

And tried to run ./vsock_test (client in the guest, server in the host), I had the following crash:

Control socket connected to 192.168.1.1:12345.                          
0 - SOCK_STREAM connection reset...                                     
[    8.050215] BUG: kernel NULL pointer derefer                         
[    8.050960] #PF: supervisor read access in kernel mode               
[    8.050960] #PF: error_code(0x0000) - not-present page               
[    8.050960] PGD 0 P4D 0                                              
[    8.050960] Oops: 0000 [#1] PREEMPT SMP PTI                          
[    8.050960] CPU: 0 PID: 109 Comm: vsock_test Not tainted 6.4.0-rc3-gd707c220a700
[    8.050960] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14
[    8.050960] RIP: 0010:static_key_count+0x0/0x20                      
[    8.050960] Code: 04 4c 8b 46 08 49 29 c0 4c 01 c8 4c 89 47 08 89 0e 89 56 04 4f
[    8.050960] RSP: 0018:ffffa9a1c021bdc0 EFLAGS: 00010202              
[    8.050960] RAX: ffffffffac309880 RBX: ffffffffc02fc140 RCX: 0000000000000000
[    8.050960] RDX: ffff9a5eff944600 RSI: 0000000000000000 RDI: 0000000000000000
[    8.050960] RBP: ffff9a5ec2371900 R08: ffffa9a1c021bd30 R09: ffff9a5eff98e0c0
[    8.050960] R10: 0000000000001000 R11: 0000000000000000 R12: ffffa9a1c021be80
[    8.050960] R13: 0000000000000000 R14: 0000000000000002 R15: ffff9a5ec1cfca80
[    8.050960] FS:  00007fa9bf88c5c0(0000) GS:ffff9a5efe400000(0000) knlGS:00000000
[    8.050960] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033        
[    8.050960] CR2: 0000000000000000 CR3: 00000000023e0000 CR4: 00000000000006f0
[    8.050960] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    8.050960] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    8.050960] Call Trace:                                              
[    8.050960]  <TASK>                                                  
[    8.050960]  once_deferred+0xd/0x30                                  
[    8.050960]  vsock_assign_transport+0xa2/0x1b0 [vsock]               
[    8.050960]  vsock_connect+0xb4/0x3a0 [vsock]                        
[    8.050960]  ? var_wake_function+0x60/0x60                           
[    8.050960]  __sys_connect+0x9e/0xd0                                 
[    8.050960]  ? _raw_spin_unlock_irq+0xe/0x30                         
[    8.050960]  ? do_setitimer+0x128/0x1f0                              
[    8.050960]  ? alarm_setitimer+0x4c/0x90                             
[    8.050960]  ? fpregs_assert_state_consistent+0x1d/0x50              
[    8.050960]  ? exit_to_user_mode_prepare+0x36/0x130                  
[    8.050960]  __x64_sys_connect+0x11/0x20                             
[    8.050960]  do_syscall_64+0x3b/0xc0                                 
[    8.050960]  entry_SYSCALL_64_after_hwframe+0x4b/0xb5                
[    8.050960] RIP: 0033:0x7fa9bf7c4d13                                 
[    8.050960] Code: 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 48
[    8.050960] RSP: 002b:00007ffdf2d96cc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000a
[    8.050960] RAX: ffffffffffffffda RBX: 0000560c305d0020 RCX: 00007fa9bf7c4d13
[    8.050960] RDX: 0000000000000010 RSI: 00007ffdf2d96ce0 RDI: 0000000000000004
[    8.050960] RBP: 0000000000000004 R08: 0000560c317dc018 R09: 0000000000000000
[    8.050960] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[    8.050960] R13: 0000560c305ccc2d R14: 00007ffdf2d96ce0 R15: 00007ffdf2d96d70
[    8.050960]  </TASK>  


I guess crash is somewhere near:

old_info->transport->release(vsk); in vsock_assign_transport(). May be my config is wrong...

Thanks, Arseniy