media: venus: fix use after free in vdec_close

There appears to be a possible use after free with vdec_close().
The firmware will add buffer release work to the work queue through
HFI callbacks as a normal part of decoding. Randomly closing the
decoder device from userspace during normal decoding can incur
a read after free for inst.

Fix it by cancelling the work in vdec_close.

Cc: stable@vger.kernel.org
Fixes: af2c3834 ("[media] media: venus: adding core part and helper functions")
Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
Acked-by: Vikash Garodia <quic_vgarodia@quicinc.com>
Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/platform/qcom/venus/vdec.c

@@ -1747,6 +1747,7 @@ static int vdec_close(struct file *file)
 
 	vdec_pm_get(inst);
 
+	cancel_work_sync(&inst->delayed_process_work);
 	v4l2_m2m_ctx_release(inst->m2m_ctx);
 	v4l2_m2m_release(inst->m2m_dev);
 	vdec_ctrl_deinit(inst);