linux-kernel - [PATCH] video: fbdev: udlfb: Fix use after free on dlfb_usb

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Date:   Fri, 11 Aug 2017 15:59:01 +0300
From:   Anton Vasilyev <vasilyev@...ras.ru>
To:     Bernie Thompson <bernie@...gable.com>
Cc:     Anton Vasilyev <vasilyev@...ras.ru>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ldv-project@...uxtesting.org
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 <vasilyev@...ras.ru>
---
 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