ALSA: hda: Abort capability probe at invalid register read

BugLink: http://bugs.launchpad.net/bugs/1731951
commit 098a0a62c1554f5a3813ef1b8539563214ada8f6 upstream.

The loop in snd_hdac_bus_parse_capabilities() may go to nirvana when
it hits an invalid register value read:

 BUG: unable to handle kernel paging request at ffffad5dc41f3fff
 IP: pci_azx_readl+0x5/0x10 [snd_hda_intel]
 Call Trace:
  snd_hdac_bus_parse_capabilities+0x3c/0x1f0 [snd_hda_core]
  azx_probe_continue+0x7d5/0x940 [snd_hda_intel]
  .....

This happened on a new Intel machine, and we need to check the value
and abort the loop accordingly.

[Note: the fixes tag below indicates only the commit where this patch
 can be applied; the original problem was introduced even before that
 commit]

Fixes: 6720b38420a0 ("ALSA: hda - move bus_parse_capabilities to core")
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/sound/hda/hdac_controller.c b/sound/hda/hdac_controller.c
index 978dc1801b3aceb8e2245b819097954c76595d77..f6d2985b2520cf1130a9a6c7d05781b6eafd44fb 100644 (file)
--- a/sound/hda/hdac_controller.c
+++ b/sound/hda/hdac_controller.c
@@ -284,6 +284,11 @@ int snd_hdac_bus_parse_capabilities(struct hdac_bus *bus)
                dev_dbg(bus->dev, "HDA capability ID: 0x%x\n",
                        (cur_cap & AZX_CAP_HDR_ID_MASK) >> AZX_CAP_HDR_ID_OFF);
 
+               if (cur_cap == -1) {
+                       dev_dbg(bus->dev, "Invalid capability reg read\n");
+                       break;
+               }
+
                switch ((cur_cap & AZX_CAP_HDR_ID_MASK) >> AZX_CAP_HDR_ID_OFF) {
                case AZX_ML_CAP_ID:
                        dev_dbg(bus->dev, "Found ML capability\n");