2017-08-11 12:59:10

by Anton Vasilyev

[permalink] [raw]
Subject: [PATCH] video: fbdev: udlfb: Fix use after free on dlfb_usb_probe error path

If dlfb_usb_probe drops to error path then there is only one
kref_init() call and no kref_get(), so second kref_put() leads to
use after free.

The patch removes superfluous kref_put on dlfb_usb_probe error path.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Anton Vasilyev <[email protected]>
---
drivers/video/fbdev/udlfb.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c
index 05ef657..f71b49f 100644
--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c
@@ -1655,7 +1655,6 @@ static int dlfb_usb_probe(struct usb_interface *interface,
error:
if (dev) {

- kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */
kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */

/* dev has been deallocated. Do not dereference */
--
2.7.4


Subject: Re: [PATCH] video: fbdev: udlfb: Fix use after free on dlfb_usb_probe error path

On Friday, August 11, 2017 03:59:01 PM Anton Vasilyev wrote:
> If dlfb_usb_probe drops to error path then there is only one
> kref_init() call and no kref_get(), so second kref_put() leads to
> use after free.
>
> The patch removes superfluous kref_put on dlfb_usb_probe error path.
>
> Found by Linux Driver Verification project (linuxtesting.org).
>
> Signed-off-by: Anton Vasilyev <[email protected]>

Patch queued for 4.14, thanks.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics