RE: [PATCH v3 3/3] Drivers: hv: vmbus: Fix race condition with new ring_buffer_info mutex

[Michael Kelley]

From: Kimberly Brown <kimbrownkd@xxxxxxxxx> Sent: Thursday, March 14, 2019 1:05 PM
> 
> Fix a race condition that can result in a ring buffer pointer being set
> to null while a "_show" function is reading the ring buffer's data. This
> problem was discussed here: https://lkml.org/lkml/2018/10/18/779
> 
> To fix the race condition, add a new mutex lock to the
> "hv_ring_buffer_info" struct. Add a new function,
> "hv_ringbuffer_pre_init()", where a channel's inbound and outbound
> ring_buffer_info mutex locks are initialized.
> 
> Acquire/release the locks in the "hv_ringbuffer_cleanup()" function,
> which is where the ring buffer pointers are set to null.
> 
> Acquire/release the locks in the four channel-level "_show" functions
> that access ring buffer data. Remove the "const" qualifier from the
> "vmbus_channel" parameter and the "rbi" variable of the channel-level
> "_show" functions so that the locks can be acquired/released in these
> functions.
> 
> Acquire/release the locks in hv_ringbuffer_get_debuginfo(). Remove the
> "const" qualifier from the "hv_ring_buffer_info" parameter so that the
> locks can be acquired/released in this function.
> 
> Signed-off-by: Kimberly Brown <kimbrownkd@xxxxxxxxx>

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>