[alsa-devel] [PATCH] ALSA: hda: Abort capability probe at invalid register read

[Takashi Iwai]

On Tue, 17 Oct 2017 19:15:08 +0200,
Vinod Koul wrote:
> 
> On Tue, Oct 17, 2017 at 04:47:11PM +0200, Takashi Iwai wrote:
> > 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.
> 
> okay and what machine is the problem here. I have had a similar bug report
> from Gfx CI guys on  CFL machine. Turns out the BIOS was buggy and we fixed
> that up by upgrading the BIOS.

Yes, it's a CFL-H.  Possibly a buggy BIOS, but the driver still
shouldn't crash.

> Yes it is a good idea to keep this guard but -1 would mean that HW read is
> failing which points to some other issue here

Right.


Takashi

> > [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")
> > Cc: <stable at vger.kernel.org>
> > Signed-off-by: Takashi Iwai <tiwai at suse.de>
> > ---
> >  sound/hda/hdac_controller.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/sound/hda/hdac_controller.c b/sound/hda/hdac_controller.c
> > index 978dc1801b3a..f6d2985b2520 100644
> > --- 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");
> > -- 
> > 2.14.2
> > 
> 
> -- 
> ~Vinod
>