On Thu, Dec 02, 2021 at 04:32:14PM +0100, Vincent Whitchurch wrote:
> The driver currently assumes that the notify callback is only received
> when the device is done with all the queued buffers.
>
> However, this is not true, since the notify callback could be called
> without any of the queued buffers being completed (for example, with
> virtio-pci and shared interrupts) or with only some of the buffers being
> completed (since the driver makes them available to the device in
> multiple separate virtqueue_add_sgs() calls).
>
> This can lead to incorrect data on the I2C bus or memory corruption in
> the guest if the device operates on buffers which are have been freed by
> the driver. (The WARN_ON in the driver is also triggered.)
>
> BUG kmalloc-128 (Tainted: G W ): Poison overwritten
> First byte 0x0 instead of 0x6b
> Allocated in i2cdev_ioctl_rdwr+0x9d/0x1de age=243 cpu=0 pid=28
> memdup_user+0x2e/0xbd
> i2cdev_ioctl_rdwr+0x9d/0x1de
> i2cdev_ioctl+0x247/0x2ed
> vfs_ioctl+0x21/0x30
> sys_ioctl+0xb18/0xb41
> Freed in i2cdev_ioctl_rdwr+0x1bb/0x1de age=68 cpu=0 pid=28
> kfree+0x1bd/0x1cc
> i2cdev_ioctl_rdwr+0x1bb/0x1de
> i2cdev_ioctl+0x247/0x2ed
> vfs_ioctl+0x21/0x30
> sys_ioctl+0xb18/0xb41
>
> Fix this by calling virtio_get_buf() from the notify handler like other
> virtio drivers and by actually waiting for all the buffers to be
> completed.
>
> Fixes: 3cfc88380413d20f ("i2c: virtio: add a virtio i2c frontend driver")
> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Applied to for-current, thanks!
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