Forwarded: [PATCH] media: gspca: don't call stopN/stop0 after device disconnect

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***

Subject: [PATCH] media: gspca: don't call stopN/stop0 after device disconnect
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

gspca_stream_off() calls the sub-driver's stopN() and stop0()
callbacks unconditionally. These issue USB requests using
gspca_dev->dev, which becomes a dangling pointer once the USB device
has been disconnected and freed, causing a use-after-free when the
video device fd is closed after disconnect.

Add a gspca_dev->present check before calling stopN() and stop0(),
matching the existing check already used for gspca_input_create_urb()
in the same function.

Reported-by: syzbot+537b5eb78cebbff5ea70@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=537b5eb78cebbff5ea70
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 drivers/media/usb/gspca/gspca.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/gspca/gspca.c b/drivers/media/usb/gspca/gspca.c
index 594d73e50b9f..5c33cf397f3d 100644
--- a/drivers/media/usb/gspca/gspca.c
+++ b/drivers/media/usb/gspca/gspca.c
@@ -733,14 +733,14 @@ static void gspca_stream_off(struct gspca_dev *gspca_dev)
 {
 	gspca_dev->streaming = false;
 	gspca_dev->usb_err = 0;
-	if (gspca_dev->sd_desc->stopN)
+	if (gspca_dev->present && gspca_dev->sd_desc->stopN)
 		gspca_dev->sd_desc->stopN(gspca_dev);
 	destroy_urbs(gspca_dev);
 	gspca_input_destroy_urb(gspca_dev);
 	gspca_set_alt0(gspca_dev);
 	if (gspca_dev->present)
 		gspca_input_create_urb(gspca_dev);
-	if (gspca_dev->sd_desc->stop0)
+	if (gspca_dev->present && gspca_dev->sd_desc->stop0)
 		gspca_dev->sd_desc->stop0(gspca_dev);
 	gspca_dbg(gspca_dev, D_STREAM, "stream off OK\n");
 }
-- 
2.43.0