On Tue, Oct 17, 2017 at 07:15:08PM +0200, Takashi Iwai wrote:
> 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.
Okay so can you ask them to update BIOS and check.
> > 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.
In this case should we send this to stable? I have not seen this crashing
till now except bad BIOS issue
>
>
> 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
> >
--
~Vinod
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