mailbox: pcc: Free the channel before unmapping the shared memory

I am seeing a crash on PCC that is related to a an shared memory being
unmapped before the IRQ is disabled, and the IRQ kicks in and hits the
unmapped (NULL) address. This is a summary of what I see on my box:

	scmi_protocol scmi_dev.1: Message for 1 type 0 is not expected!
	Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004
	 __handle_irq_event_percpu+0x1c4/0x9e0
	 handle_irq_event+0x98/0x218
	 handle_fasteoi_irq+0x230/0x750
	 generic_handle_domain_irq+0xac/0x138
	 gic_handle_irq+0x344/0x740
	 call_on_irq_stack+0x30/0x48

The trapping store is iowrite32(SCMI_SHMEM_FLAG_INTR_ENABLED,
&shmem->header.flags), a write of 1 at offset 4 of a NULL base.

But, back to the problem, pcc_mbox_free_channel() unmaps the shared
memory and clears pchan->chan.shmem *before* freeing the IRQ (aka
calling mbox_free_channel()).

The interrupt is still live when the mapping goes away.

Free the channel first, before the memory unmap. mbox_free_channel()
calls pcc_shutdown(), which frees the platform interrupt, and then unmap
shared memory.

Fixes: 7f9e19f207be ("mailbox: pcc: Check before sending MCTP PCC response ACK")
Reviewed-by: Sudeep Holla <sudeep.holla@kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

0 files changed, 0 insertions, 0 deletions