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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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