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@xxxxxxxxxxxxxxx>
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> > ---
> > 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
>
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