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* [PATCH] Drivers: hv: vmbus: Fix kernel crash upon unbinding a device from uio_hv_generic driver
@ 2021-08-31 14:39 Vitaly Kuznetsov
  2021-09-01 11:25 ` Wei Liu
                   ` (3 more replies)
  0 siblings, 4 replies; 6+ messages in thread
From: Vitaly Kuznetsov @ 2021-08-31 14:39 UTC (permalink / raw)
  To: linux-hyperv
  Cc: Andres Beltran, Michael Kelley, Andrea Parri (Microsoft),
	Dexuan Cui, Wei Liu, Stephen Hemminger, Haiyang Zhang,
	K. Y. Srinivasan, linux-kernel

The following crash happens when a never-used device is unbound from
uio_hv_generic driver:

 kernel BUG at mm/slub.c:321!
 invalid opcode: 0000 [#1] SMP PTI
 CPU: 0 PID: 4001 Comm: bash Kdump: loaded Tainted: G               X --------- ---  5.14.0-0.rc2.23.el9.x86_64 #1
 Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008  12/07/2018
 RIP: 0010:__slab_free+0x1d5/0x3d0
 Call Trace:
  ? pick_next_task_fair+0x18e/0x3b0
  ? __cond_resched+0x16/0x40
  ? vunmap_pmd_range.isra.0+0x154/0x1c0
  ? __vunmap+0x22d/0x290
  ? hv_ringbuffer_cleanup+0x36/0x40 [hv_vmbus]
  ? hv_uio_remove+0x43/0x60 [uio_hv_generic]
  hv_ringbuffer_cleanup+0x36/0x40 [hv_vmbus]
  vmbus_free_ring+0x21/0x60 [hv_vmbus]
  hv_uio_remove+0x4f/0x60 [uio_hv_generic]
  vmbus_remove+0x23/0x30 [hv_vmbus]

The problem appears to be that we free 'ring_info->pkt_buffer' twice:
first, when the device is unbound from in-kernel driver (netvsc in this
case) and second from hv_uio_remove(). Normally, ring buffer is supposed
to be re-initialized from hv_uio_open() but this happens when UIO device
is being opened and this is not guaranteed to happen.

Generally, it is OK to call hv_ringbuffer_cleanup() twice for the same
channel (which is being handed over between in-kernel drivers and UIO) even
if we didn't call hv_ringbuffer_init() in between. We, however, need to
avoid kfree() call for an already freed pointer.

Fixes: adae1e931acd ("Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer")
Signed-off-by: Vitaly Kuznetsov <>
 drivers/hv/ring_buffer.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 2aee356840a2..314015d9e912 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -245,6 +245,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
+	ring_info->pkt_buffer = NULL;
 	ring_info->pkt_buffer_size = 0;

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2021-09-03 11:00 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-31 14:39 [PATCH] Drivers: hv: vmbus: Fix kernel crash upon unbinding a device from uio_hv_generic driver Vitaly Kuznetsov
2021-09-01 11:25 ` Wei Liu
2021-09-01 11:40   ` Vitaly Kuznetsov
2021-09-01 15:25 ` Andrea Parri
2021-09-02 17:09 ` Michael Kelley
2021-09-03 11:00 ` Wei Liu

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