[PATCH] media: Fix invalid link creation when source entity has 0 pads

[gshahrouzi]

>From 307209d175be0145e36b9cf95944e2e62afeab11 Mon Sep 17 00:00:00 2001
From: Gabriel Shahrouzi <gshahrouzi@xxxxxxxxx>
Date: Mon, 24 Mar 2025 19:45:55 -0400
Subject: [PATCH] media: Fix invalid link creation when source entity has 0
 pads

This patch addresses the warning triggered in the media_create_pad_link()
function, specifically related to the check WARN_ON(source_pad >=
source->num_pads). The fix proposed adds an additional check to ensure that
source->num_pads is non-zero before proceeding with the
media_create_pad_link() function.

Reported-by: syzbot+701fc9cc0cb44e2b0fe9@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=701fc9cc0cb44e2b0fe9
Tested-by: syzbot+701fc9cc0cb44e2b0fe9@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: a3fbc2e6bb05 ("media: mc-entity.c: use WARN_ON, validate link pads")
Signed-off-by: Gabriel Shahrouzi <gshahrouzi@xxxxxxxxx>
---
 drivers/media/usb/uvc/uvc_entity.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/uvc/uvc_entity.c b/drivers/media/usb/uvc/uvc_entity.c
index cc68dd24eb42..5397ce76c218 100644
--- a/drivers/media/usb/uvc/uvc_entity.c
+++ b/drivers/media/usb/uvc/uvc_entity.c
@@ -43,7 +43,7 @@ static int uvc_mc_create_links(struct uvc_video_chain *chain,
 		source = (UVC_ENTITY_TYPE(remote) == UVC_TT_STREAMING)
 		       ? (remote->vdev ? &remote->vdev->entity : NULL)
 		       : &remote->subdev.entity;
-		if (source == NULL)
+		if (source == NULL || source->num_pads == 0)
 			continue;
 
 		remote_pad = remote->num_pads - 1;
-- 
2.43.0