linux-kernel - Re: [PATCH] mtd: fix use-after-free in mtd release

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Message-ID: <20230727172013.7c85c05d@xps-13>
Date:   Thu, 27 Jul 2023 17:20:13 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Alexander Usyskin <alexander.usyskin@...el.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tomas Winkler <tomas.winkler@...el.com>,
        Vitaly Lubart <vitaly.lubart@...el.com>,
        Zhang Xiaoxu <zhangxiaoxu5@...wei.com>
Subject: Re: [PATCH] mtd: fix use-after-free in mtd release

Hi Andy,

andriy.shevchenko@...ux.intel.com wrote on Thu, 27 Jul 2023 18:12:04
+0300:

> On Thu, Jul 27, 2023 at 05:57:58PM +0300, Alexander Usyskin wrote:
> > I case of partition device_unregister in mtd_device_release  
> 
> In
> 
> device_unregister()
> mtd_device_release()
> 
> > calls mtd_release which frees mtd_info structure for partition.  
> 
> mtd_release()
> 
> > All code after device_unregister in mtd_device_release thus  
> 
> device_unregister()
> mtd_device_release()
> 
> > works already freed memory.  
> 
> uses?
> 
> > Move part of code to mtd_release and restict mtd->dev cleanup  
> 
> mtd_release()

Yup, thanks for all these suggestions, I agree with them.

> > to non-partion object.
> > For partition object such cleanup have no sense as partition
> > mtd_info is removed.
> > 
> > Cc: Miquel Raynal <miquel.raynal@...tlin.com>
> > Cc: Zhang Xiaoxu <zhangxiaoxu5@...wei.com>
> > Fixes: 19bfa9ebebb5 ("mtd: use refcount to prevent corruption")  
> 
> Closes: ?

Did I miss a recent update on the use of Fixes? I thought Closes was
supposed to point at a bug report while Fixes would point to the faulty
commit. Right now I feel like Fixes is the right tag, but if you have a
source explaining why we should not longer do it like I am used to,
I would appreciate a link.

Thanks,
Miquèl