Re: Need help in debugging "memory leak in em28xx_init_dev"

[Pavel Skripkin <paskripkin@gmail.com>]

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On 11/1/21 06:02, Dongliang Mu wrote:
> Hi all,
> 
> My local syzkaller instance found one bug named "memory leak in
> em28xx_init_dev" in 5.14-rc5. Kernel configuration and PoC file are
> attached(I don't check if the latest kernel is vulnerable, but it
> should be). The trace from memleak is as follows:
> 
> backtrace:
>      [<ffffffff842cc66d>] kmalloc include/linux/slab.h:591 [inline]
>      [<ffffffff842cc66d>] kzalloc include/linux/slab.h:721 [inline]
>      [<ffffffff842cc66d>] em28xx_media_device_init
> drivers/media/usb/em28xx/em28xx-cards.c:3444 [inline]
>      [<ffffffff842cc66d>] em28xx_init_dev.isra.0+0x366/0x9bf
> drivers/media/usb/em28xx/em28xx-cards.c:3624
>      [<ffffffff842cd1bd>] em28xx_usb_probe.cold+0x4f7/0xf95
> drivers/media/usb/em28xx/em28xx-cards.c:3979
>      [<ffffffff82bf0815>] usb_probe_interface+0x185/0x350
> drivers/usb/core/driver.c:396
> 


Looks like missing clean up on error handling path.

->probe()
     em28xx_init_dev()
       em28xx_media_device_init() <- dev->media_dev allocated
       *error somewhere in em28xx_init_dev()*


And then nothing unwinds em28xx_media_device_init() call, since 
disconnect won't be called in case of failure in ->probe()


Just build tested, but, I guess, something like this should work.



With regards,
Pavel Skripkin




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diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index c1e0dccb7408..f22e5ca2d1b3 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -3626,7 +3626,7 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
 	if (dev->is_audio_only) {
 		retval = em28xx_audio_setup(dev);
 		if (retval)
-			return -ENODEV;
+			goto deinit_media;
 		em28xx_init_extension(dev);
 
 		return 0;
@@ -3645,7 +3645,7 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
 		dev_err(&dev->intf->dev,
 			"%s: em28xx_i2c_register bus 0 - error [%d]!\n",
 		       __func__, retval);
-		return retval;
+		goto deinit_media;
 	}
 
 	/* register i2c bus 1 */
@@ -3663,7 +3663,7 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
 
 			em28xx_i2c_unregister(dev, 0);
 
-			return retval;
+			goto deinit_media;
 		}
 	}
 
@@ -3671,6 +3671,10 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
 	em28xx_card_setup(dev);
 
 	return 0;
+
+deinit_media:
+	em28xx_unregister_media_device(dev);
+	return retval;
 }
 
 static int em28xx_duplicate_dev(struct em28xx *dev)