[linux-yocto] [linux-yocto v5.0/standard/base][PATCH] ALSA: hda: check RIRB to avoid use NULL pointer

[Liwei Song]

Fix the following BUG:

BUG: unable to handle kernel NULL pointer dereference at 000000000000000c
Workqueue: events azx_probe_work [snd_hda_intel]
RIP: 0010:snd_hdac_bus_update_rirb+0x80/0x160 [snd_hda_core]
Call Trace:
 <IRQ>
 azx_interrupt+0x78/0x140 [snd_hda_codec]
 __handle_irq_event_percpu+0x49/0x300
 handle_irq_event_percpu+0x23/0x60
 handle_irq_event+0x3c/0x60
 handle_edge_irq+0xdb/0x180
 handle_irq+0x23/0x30
 do_IRQ+0x6a/0x140
 common_interrupt+0xf/0xf

The Call Trace happened when run kdump on a NFS rootfs system.
Exist the following calling sequence when boot the second kernel:

azx_first_init()
   --> azx_acquire_irq()
                      <-- interrupt come in, azx_interrupt() was called
   --> hda_intel_init_chip()
      --> azx_init_chip()
         --> snd_hdac_bus_init_chip()
              --> snd_hdac_bus_init_cmd_io();
                    --> init rirb.buf and corb.buf

Interrupt happened after azx_acquire_irq() while RIRB still didn't got
initialized, then NULL pointer will be used when process the interrupt.

Considering adjust the calling sequence may import new issue like
2eeeb4f4733b ("ASoC: Intel: Skylake: Acquire irq after RIRB allocation")
so here simply check the value of RIRB to avoid using NULL pointer.

Fixes: 14752412721c ("ALSA: hda - Add the controller helper codes to hda-core module")
Signed-off-by: Liwei Song <liwei.song at windriver.com>
---
 sound/hda/hdac_controller.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/hda/hdac_controller.c b/sound/hda/hdac_controller.c
index 74244d8e2909..2f0fa5353361 100644
--- a/sound/hda/hdac_controller.c
+++ b/sound/hda/hdac_controller.c
@@ -195,6 +195,9 @@ void snd_hdac_bus_update_rirb(struct hdac_bus *bus)
 		return;
 	bus->rirb.wp = wp;
 
+	if (!bus->rirb.buf)
+		return;
+
 	while (bus->rirb.rp != wp) {
 		bus->rirb.rp++;
 		bus->rirb.rp %= AZX_MAX_RIRB_ENTRIES;
-- 
2.7.4