[PATCH] ALSA: hda: Don't free card at probe error in vga_switcheroo handler

[PATCH] ALSA: hda: Don't free card at probe error in vga_switcheroo handler

[Takashi Iwai]

The vga_switcheroo handler azx_vs_set_state() calls
azx_probe_contine() for enabling the audio, and if an error happens
during the probe, azx_probe_continue() releases its associated sound
card object at the error path.  The card release procedure includes
the call of vga_switcheroo_unregister_client(), and this triggers the
vgasr_mutex lock again that had been already held by the caller
(vga_switcheroo_process_delayed_switch()) -- leading to a deadlock.

(Moreover, the card release will cause a potential UAF at the error
message in azx_vs_set_state() since the card object is already gone;
this was the original report by Sashiko.)

For avoiding the unneeded crash, it's better to avoid the card release
in this error path, so we make azx_probe_continue() behaving
conditionally.  In return, set hda->init_failed flag, so that any
further (re-)attempts will be filtered after that point.

The check of hda->init_failed is dropped from azx_vs_can_switch().
It's because otherwise vga_switcheroo can't be switched to turn off
GPU once when a probe error happens at the audio side.

Fixes: 39173303c838 ("ALSA: hda: Free card instance properly at probe errors")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20261007213728.155092-1-tiwai%40suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/hda/controllers/intel.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/sound/hda/controllers/intel.c b/sound/hda/controllers/intel.c
index 24015c73a67f..5d989e57b128 100644
--- a/sound/hda/controllers/intel.c
+++ b/sound/hda/controllers/intel.c
@@ -1184,7 +1184,7 @@ static const struct dev_pm_ops azx_pm = {
 };
 
 
-static int azx_probe_continue(struct azx *chip);
+static int azx_probe_continue(struct azx *chip, bool free_on_error);
 
 #ifdef SUPPORT_VGA_SWITCHEROO
 static struct pci_dev *get_bound_vga(struct pci_dev *pci);
@@ -1211,8 +1211,10 @@ static void azx_vs_set_state(struct pci_dev *pci,
 		if (!disabled) {
 			dev_info(chip->card->dev,
 				 "Start delayed initialization\n");
-			if (azx_probe_continue(chip) < 0)
+			if (azx_probe_continue(chip, false) < 0) {
+				hda->init_failed = 1;
 				dev_err(chip->card->dev, "initialization error\n");
+			}
 		}
 	} else {
 		dev_info(chip->card->dev, "%s via vga_switcheroo\n",
@@ -1251,8 +1253,6 @@ static bool azx_vs_can_switch(struct pci_dev *pci)
 	struct hda_intel *hda = container_of(chip, struct hda_intel, chip);
 
 	wait_for_completion(&hda->probe_wait);
-	if (hda->init_failed)
-		return false;
 	if (chip->disabled || !hda->probe_continued)
 		return true;
 	if (snd_hda_lock_devices(&chip->bus))
@@ -1738,7 +1738,7 @@ static void azx_check_snoop_available(struct azx *chip)
 static void azx_probe_work(struct work_struct *work)
 {
 	struct hda_intel *hda = container_of(work, struct hda_intel, probe_work.work);
-	azx_probe_continue(&hda->chip);
+	azx_probe_continue(&hda->chip, true);
 }
 
 static int default_bdl_pos_adj(struct azx *chip)
@@ -2356,7 +2356,7 @@ static const unsigned int azx_max_codecs[AZX_NUM_DRIVERS] = {
 	[AZX_DRIVER_TERA] = 1,
 };
 
-static int azx_probe_continue(struct azx *chip)
+static int azx_probe_continue(struct azx *chip, bool free_on_error)
 {
 	struct hda_intel *hda = container_of(chip, struct hda_intel, chip);
 	struct hdac_bus *bus = azx_bus(chip);
@@ -2447,8 +2447,10 @@ static int azx_probe_continue(struct azx *chip)
 
 out_free:
 	if (err < 0) {
-		pci_set_drvdata(pci, NULL);
-		snd_card_free(chip->card);
+		if (free_on_error) {
+			pci_set_drvdata(pci, NULL);
+			snd_card_free(chip->card);
+		}
 		return err;
 	}
 
-- 
2.55.0