[PATCH 6.18 218/396] ALSA: usb-audio: Clamp frame size in implicit-feedback mode

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

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

From: Sonali Pradhan <[email protected]>

commit 8d7a30c50c2e58a6839634ed0acde14466d1dc61 upstream.

snd_usb_handle_sync_urb() scales received sync packet sizes by the sender's
stride and stores the result directly in out_packet->packet_size[i]. If a
connected USB device sends an oversized sync packet, this frame count can
exceed ep->maxframesize.

The un-clamped frame count then propagates to the playback endpoint queue,
potentially driving packet transfers beyond the endpoint's hardware frame
limits.

Cap the calculated frame count against ep->maxframesize in
snd_usb_handle_sync_urb() to prevent oversized packets from entering the
playback queue.

Fixes: 28acb12014fb ("ALSA: usb-audio: use sender stride for implicit feedback")
Cc: [email protected]
Assisted-by: Jetski:Gemini-3.6-Flash
Signed-off-by: Sonali Pradhan <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 sound/usb/endpoint.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -1806,11 +1806,13 @@ static void snd_usb_handle_sync_urb(stru
 
 		out_packet->packets = in_ctx->packets;
 		for (i = 0; i < in_ctx->packets; i++) {
-			if (urb->iso_frame_desc[i].status == 0)
-				out_packet->packet_size[i] =
+			if (urb->iso_frame_desc[i].status == 0) {
+				unsigned int frames =
 					urb->iso_frame_desc[i].actual_length / sender->stride;
-			else
+				out_packet->packet_size[i] = min(frames, ep->maxframesize);
+			} else {
 				out_packet->packet_size[i] = 0;
+			}
 		}
 
 		spin_unlock_irqrestore(&ep->lock, flags);