Re: [PATCH] scsi: storvsc: Fix a race in sub-channel creation that can cause panic

KY,

From: Dexuan Cui decui@microsoft.com

We can concurrently try to open the same sub-channel from 2 paths:

path #1: vmbus_onoffer() -> vmbus_process_offer() -> handle_sc_creation(). path #2: storvsc_probe() -> storvsc_connect_to_vsp() -> -> storvsc_channel_init() -> handle_multichannel_storage() -> -> vmbus_are_subchannels_present() -> handle_sc_creation().

They conflict with each other, but it was not an issue before the recent commit ae6935ed7d42 ("vmbus: split ring buffer allocation from open"), because at the beginning of vmbus_open() we checked newchannel->state so only one path could succeed, and the other would return with -EINVAL.

Applied to 4.20/scsi-fixes. Thank you!