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 > Signed-off-by: Vincent Whitchurch Applied to for-current, thanks!