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Drivers: hv: vmbus: Fix kernel crash upon unbinding a device from uio_hv_generic driver

Vitaly Kuznetsov requested to merge vkuznets/centos-stream-9:bug1999535 into main

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1999535

commit f1940d4e9cbe6208e7e77e433c587af108152a17
Author: Vitaly Kuznetsov <vkuznets@redhat.com>
Date:   Tue Aug 31 16:39:16 2021 +0200

    Drivers: hv: vmbus: Fix kernel crash upon unbinding a device from uio_hv_generic driver

    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]
      kfree+0x331/0x380
      ? 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]
      __device_release_driver+0x17a/0x230
      device_driver_detach+0x3c/0xa0
      unbind_store+0x113/0x130
    ...

    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 <vkuznets@redhat.com>
    Reviewed-by: Andrea Parri <parri.andrea@gmail.com>
    Reviewed-by: Michael Kelley <mikelley@microsoft.com>
    Link: https://lore.kernel.org/r/20210831143916.144983-1-vkuznets@redhat.com
    Signed-off-by: Wei Liu <wei.liu@kernel.org>

Signed-off-by: Vitaly Kuznetsov vkuznets@redhat.com

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