linux-kernel - Re: [PATCH 0/2] driver core: platform: avoid use-after-free on device name

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Message-ID: <2025022005-affluent-hardcore-c595@gregkh>
Date: Thu, 20 Feb 2025 13:41:00 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Grant Likely <grant.likely@...retlab.ca>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>, Binbin Zhou <zhoubinbin@...ngson.cn>,
	linux-sound@...r.kernel.org,
	Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
	Grégory Clement <gregory.clement@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>, stable@...r.kernel.org
Subject: Re: [PATCH 0/2] driver core: platform: avoid use-after-free on
 device name

On Tue, Feb 18, 2025 at 12:00:11PM +0100, Théo Lebrun wrote:
> The use-after-free bug appears when:
>  - A platform device is created from OF, by of_device_add();
>  - The same device's name is changed afterwards using dev_set_name(),
>    by its probe for example.
> 
> Out of the 37 drivers that deal with platform devices and do a
> dev_set_name() call, only one might be affected. That driver is
> loongson-i2s-plat [0]. All other dev_set_name() calls are on children
> devices created on the spot. The issue was found on downstream kernels
> and we don't have what it takes to test loongson-i2s-plat.
> 
> Note: loongson-i2s-plat maintainers are CCed.
> 
>    ⟩ # Finding potential trouble-makers:
>    ⟩ git grep -l 'struct platform_device' | xargs grep -l dev_set_name
> 
> The solution proposed is to add a flag to platform_device that tells if
> it is responsible for freeing its name. We can then duplicate the
> device name inside of_device_add() instead of copying the pointer.

Ick.

> What is done elsewhere?
>  - Platform bus code does a copy of the argument name that is stored
>    alongside the struct platform_device; see platform_device_alloc()[1].
>  - Other busses duplicate the device name; either through a dynamic
>    allocation [2] or through an array embedded inside devices [3].
>  - Some busses don't have a separate name; when they want a name they
>    take it from the device [4].

Really ick.

Let's do the right thing here and just get rid of the name pointer
entirely in struct platform_device please.  Isn't that the correct
thing that way the driver core logic will work properly for all of this.

thanks,

greg k-h