From 14948e39445db674516ccabdf01090586ecfdc9b Mon Sep 17 00:00:00 2001 From: Kimberly Brown Date: Thu, 14 Mar 2019 16:05:15 -0400 Subject: Drivers: hv: vmbus: Fix race condition with new ring_buffer_info mutex 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 Reviewed-by: Michael Kelley Signed-off-by: Sasha Levin --- include/linux/hyperv.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'include/linux/hyperv.h') diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 64698ec8f2ac..8b9a93c99c9b 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -141,6 +141,11 @@ struct hv_ring_buffer_info { u32 ring_datasize; /* < ring_size */ u32 priv_read_index; + /* + * The ring buffer mutex lock. This lock prevents the ring buffer from + * being freed while the ring buffer is being accessed. + */ + struct mutex ring_buffer_mutex; }; @@ -1206,7 +1211,7 @@ struct hv_ring_buffer_debug_info { }; -int hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info, +int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, struct hv_ring_buffer_debug_info *debug_info); /* Vmbus interface */ -- cgit