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Drivers: hv: vmbus: Fix race condition with new ring_buffer_info mutex

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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@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kimberly Brown
2019-03-14 16:05:15 -04:00
committed by Sasha Levin
parent 4713eb7b58
commit 14948e3944
5 changed files with 79 additions and 32 deletions
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7
include/linux/hyperv.h
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@@ -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 */