[PATCH v3] ALSA: usb-audio: validate full match when resolving quirk aliases

[Cássio Gabriel]

get_alias_quirk() resolves a quirk for an aliased USB ID by scanning
usb_audio_ids[], but it currently checks only the vendor/product pair.

This is weak for quirk table entries that also depend on additional
USB_DEVICE_ID match fields, such as device or interface class,
subclass, protocol, interface number, or bcdDevice range.

Keep the aliased vid:pid as the lookup key, then validate only the
remaining match criteria of each candidate entry against the real
device/interface descriptors by clearing USB_DEVICE_ID_MATCH_DEVICE
from a temporary copy and passing it to usb_match_one_id().

Suggested-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@xxxxxxxxx>
---
Changes in v3:
- rework alias quirk matching as suggested by Takashi Iwai
- drop the explicit per-field helper
- keep the aliased vid:pid check first
- clear USB_DEVICE_ID_MATCH_DEVICE from a temporary id copy
- Link to v2: https://lore.kernel.org/r/20260317-alsa-usb-fix-quirk-alias-v2-1-6e531c67f0c8@xxxxxxxxx

Changes in v2:
- drop the temporary usb_device_id reconstruction approach
- validate only the remaining match_flags explicitly
- pass struct usb_interface * to get_alias_quirk()
- Link to v1: https://lore.kernel.org/r/20260314-alsa-usb-fix-quirk-alias-v1-1-3269998f7ada@xxxxxxxxx
---
 sound/usb/card.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index fd81f32a66fb..f42d72cd0378 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -866,19 +866,25 @@ static void find_last_interface(struct snd_usb_audio *chip)
 
 /* look for the corresponding quirk */
 static const struct snd_usb_audio_quirk *
-get_alias_quirk(struct usb_device *dev, unsigned int id)
+get_alias_quirk(struct usb_interface *intf, unsigned int id)
 {
 	const struct usb_device_id *p;
+	struct usb_device_id match_id;
 
 	for (p = usb_audio_ids; p->match_flags; p++) {
-		/* FIXME: this checks only vendor:product pair in the list */
-		if ((p->match_flags & USB_DEVICE_ID_MATCH_DEVICE) ==
-		    USB_DEVICE_ID_MATCH_DEVICE &&
-		    p->idVendor == USB_ID_VENDOR(id) &&
-		    p->idProduct == USB_ID_PRODUCT(id))
-			return (const struct snd_usb_audio_quirk *)p->driver_info;
-	}
+		if ((p->match_flags & USB_DEVICE_ID_MATCH_DEVICE) !=
+		     USB_DEVICE_ID_MATCH_DEVICE)
+			continue;
+		if (p->idVendor != USB_ID_VENDOR(id) ||
+		    p->idProduct != USB_ID_PRODUCT(id))
+			continue;
 
+		match_id = *p;
+		match_id.match_flags &= ~USB_DEVICE_ID_MATCH_DEVICE;
+		if (!match_id.match_flags || usb_match_one_id(intf, &match_id))
+			return (const struct snd_usb_audio_quirk *)
+				p->driver_info;
+	}
 	return NULL;
 }
 
@@ -927,7 +933,7 @@ static int usb_audio_probe(struct usb_interface *intf,
 	id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
 		    le16_to_cpu(dev->descriptor.idProduct));
 	if (get_alias_id(dev, &id))
-		quirk = get_alias_quirk(dev, id);
+		quirk = get_alias_quirk(intf, id);
 	if (quirk && quirk->ifnum >= 0 && ifnum != quirk->ifnum)
 		return -ENXIO;
 	if (quirk && quirk->ifnum == QUIRK_NODEV_INTERFACE)

---
base-commit: f803b7bb17dd19fbd84fe783683321f38834a1df
change-id: 20260313-alsa-usb-fix-quirk-alias-e9c8300ba836

Best regards,
-- 
Cássio Gabriel <cassiogabrielcontato@xxxxxxxxx>