From cb2200f7af8341aaf0c6abd7ba37e4c667c41639 Mon Sep 17 00:00:00 2001
From: Joel Pepper <joel.pepper@rwth-aachen.de>
Date: Tue, 29 May 2018 21:02:12 +0200
Subject: [PATCH] usb: gadget: uvc: configfs: Prevent format changes after linking header
Git-commit: cb2200f7af8341aaf0c6abd7ba37e4c667c41639
Patch-mainline: v4.20-rc1
References: bsc#1051510

While checks are in place to avoid attributes and children of a format
being manipulated after the format is linked into the streaming header,
the linked flag was never actually set, invalidating the protections.
Update the flag as appropriate in the header link calls.

Signed-off-by: Joel Pepper <joel.pepper@rwth-aachen.de>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/usb/gadget/function/uvc_configfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index b8763343dcae..799dc32c5bc7 100644
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -928,6 +928,7 @@ static int uvcg_streaming_header_allow_link(struct config_item *src,
 	format_ptr->fmt = target_fmt;
 	list_add_tail(&format_ptr->entry, &src_hdr->formats);
 	++src_hdr->num_fmt;
+	++target_fmt->linked;
 
 out:
 	mutex_unlock(&opts->lock);
@@ -965,6 +966,8 @@ static void uvcg_streaming_header_drop_link(struct config_item *src,
 			break;
 		}
 
+	--target_fmt->linked;
+
 out:
 	mutex_unlock(&opts->lock);
 	mutex_unlock(su_mutex);
-- 
2.16.4