RE: [PATCH 1/1] Drivers: hv: vmbus: Fix rescind handling issues

[KY Srinivasan]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> Sent: Monday, September 18, 2017 5:55 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>;
> leann.ogasawara@xxxxxxxxxxxxx; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; apw@xxxxxxxxxxxxx; olaf@xxxxxxxxx;
> marcelo.cerri@xxxxxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> jasowang@xxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH 1/1] Drivers: hv: vmbus: Fix rescind handling issues
> 
> Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> writes:
> 
> >
> > Reverting 6f3d791f300618caf82a2be0c27456edd76d5164 still helps.
> 
> In addition to the above I got the following crash while playing with
> 4.14-rc1 (unmodified):
> 
> [   55.810080] kernel tried to execute NX-protected page - exploit attempt?
> (uid: 0)
> [   55.814293] BUG: unable to handle kernel paging request at
> ffff8800059985f0
> [   55.818065] IP: 0xffff8800059985f0
> [   55.819925] PGD 22eb067 P4D 22eb067 PUD 22ec067 PMD 5f37063 PTE
> 8000000005998163
> [   55.820018] Oops: 0011 [#1] SMP
> [   55.820018] Modules linked in: vfat fat bnx2x mdio efi_pstore hv_utils
> efivars pci_hyperv ptp pps_core pcspkr hv_balloon xfs libcrc32c hv_storvsc
> hyperv_fb hv_netvsc scsi_transport_fc hid_hyperv hyperv_keyboard
> hv_vmbus
> [   55.834837] CPU: 0 PID: 498 Comm: kworker/0:2 Not tainted 4.14.0-rc1 #63
> [   55.834837] Hardware name: Microsoft Corporation Virtual Machine/Virtual
> Machine, BIOS Hyper-V UEFI Release v1.0 11/26/2012
> [   55.834837] Workqueue: events vmbus_onmessage_work [hv_vmbus]
> [   55.834837] task: ffff88003f448000 task.stack: ffffc90005398000
> [   55.834837] RIP: 0010:0xffff8800059985f0
> [   55.834837] RSP: 0018:ffffc9000539be00 EFLAGS: 00010286
> [   55.834837] RAX: ffff880005998010 RBX: ffff880005998000 RCX:
> 0000000000000000
> [   55.834837] RDX: ffff8800059985f0 RSI: 0000000000000246 RDI:
> ffff880005998000
> [   55.860040] RBP: ffffc9000539be18 R08: 00000000000002e6 R09:
> 0000000000000000
> [   55.865057] R10: ffffc9000539bdf0 R11: 000000000000a000 R12:
> 0000000000000286
> [   55.865057] R13: ffff88007ae1ed00 R14: 0000000000000000 R15:
> ffff8800065c3200
> [   55.865057] FS:  0000000000000000(0000) GS:ffff88007ae00000(0000)
> knlGS:0000000000000000
> [   55.865057] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   55.865057] CR2: ffff8800059985f0 CR3: 00000000075a5000 CR4:
> 00000000001406f0
> [   55.886745] Call Trace:
> [   55.886745]  ? vmbus_onoffer_rescind+0xfa/0x160 [hv_vmbus]
> [   55.890968]  vmbus_onmessage+0x2a/0x90 [hv_vmbus]
> [   55.891934]  vmbus_onmessage_work+0x1d/0x30 [hv_vmbus]
> [   55.891934]  process_one_work+0x193/0x390
> [   55.891934]  worker_thread+0x48/0x3c0
> [   55.891934]  kthread+0x120/0x140
> [   55.891934]  ? process_one_work+0x390/0x390
> [   55.891934]  ? kthread_create_on_node+0x60/0x60
> [   55.891934]  ret_from_fork+0x25/0x30
> [   55.891934] Code: 88 ff ff c0 85 99 05 00 88 ff ff d0 85 99 05 00 88 ff ff d0 85 99
> 05 00 88 ff ff e0 85 99 05 00 88 ff ff e0 85 99 05 00 88 ff ff <f0> 85 99 05 00 88 ff
> ff f0 85 99 05 00 88 ff ff 00 86 99 05 00
> [   55.922505] RIP: 0xffff8800059985f0 RSP: ffffc9000539be00
> [   55.922505] CR2: ffff8800059985f0
> [   55.922505] ---[ end trace 25226e00af3f94fb ]---
> [   55.933590] Kernel panic - not syncing: Fatal exception
> [   55.933590] Kernel Offset: disabled
> [   55.933590] ---[ end Kernel panic - not syncing: Fatal exception
> 
> So it seems that during
> 
> 	while (READ_ONCE(channel->probe_done) == false) {
> 		/*
>                  * We wait here until any channel offer is currently
>                  * being processed.
>                  */
>                 msleep(1);
> 	}
> 
> loop the channel disappeared. The issue may not be related to the netvsc
> hang I mentioned before. It may make sense to do refcounting for
> channels/subchannels (or employ RCU).

I will work on this issue and get you a patch to try.

K. Y
> 
> --
>   Vitaly