mailbox: qcom-cpucp: handle NULL data in send_data callback

mailbox_clear_channel() calls mbox_send_message() with NULL data to
notify the remote side that the RX channel has been cleared.
qcom_cpucp_mbox_send_data() blindly dereferenced the data pointer,
causing a NULL pointer dereference kernel panic when invoked from
this path under PREEMPT_RT.

Add an explicit NULL check and return early without writing to the
TX register, which is the correct behaviour for a channel-clear
notification.

Fixes: 0e2a9a03106c ("mailbox: Add support for QTI CPUCP mailbox controller")
Signed-off-by: Jia Yang <jia.yang@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

0 files changed, 0 insertions, 0 deletions