linux-kernel - Re: Need help in debugging "memory leak in em28xx_init

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Date:   Mon, 1 Nov 2021 10:50:07 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Dongliang Mu <mudongliangabcd@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: Need help in debugging "memory leak in em28xx_init_dev"

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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