linux-kernel - [PATCH] media: em28xx: Fix use-after-free in em28xx_alloc

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Message-Id: <20201228130205.14381-1-dinghao.liu@zju.edu.cn>
Date:   Mon, 28 Dec 2020 21:02:05 +0800
From:   Dinghao Liu <dinghao.liu@....edu.cn>
To:     dinghao.liu@....edu.cn, kjlu@....edu
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] media: em28xx: Fix use-after-free in em28xx_alloc_urbs

When kzalloc() fails, em28xx_uninit_usb_xfer() will free
usb_bufs->buf and set it to NULL. Thus the later access
to usb_bufs->buf[i] will lead to null pointer dereference.
Also the kfree(usb_bufs->buf) after that is redundant.

Fixes: d571b592c6206 ("media: em28xx: don't use coherent buffer for DMA transfers")
Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
---
 drivers/media/usb/em28xx/em28xx-core.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
index e6088b5d1b80..3daa64bb1e1d 100644
--- a/drivers/media/usb/em28xx/em28xx-core.c
+++ b/drivers/media/usb/em28xx/em28xx-core.c
@@ -956,14 +956,10 @@ int em28xx_alloc_urbs(struct em28xx *dev, enum em28xx_mode mode, int xfer_bulk,
 
 		usb_bufs->buf[i] = kzalloc(sb_size, GFP_KERNEL);
 		if (!usb_bufs->buf[i]) {
-			em28xx_uninit_usb_xfer(dev, mode);
-
 			for (i--; i >= 0; i--)
 				kfree(usb_bufs->buf[i]);
 
-			kfree(usb_bufs->buf);
-			usb_bufs->buf = NULL;
-
+			em28xx_uninit_usb_xfer(dev, mode);
 			return -ENOMEM;
 		}
 
-- 
2.17.1