linux-kernel - [PATCH 4.9 19/48] ALSA: hda: Abort capability probe at invalid register read

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Message-Id: <20171024125728.648858063@linuxfoundation.org>
Date:   Tue, 24 Oct 2017 15:03:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
        Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.9 19/48] ALSA: hda: Abort capability probe at invalid register read

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

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@...el.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/hda/hdac_controller.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/sound/hda/hdac_controller.c
+++ b/sound/hda/hdac_controller.c
@@ -284,6 +284,11 @@ int snd_hdac_bus_parse_capabilities(stru
 		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");