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

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Message-ID: <20250221094613.7b9b5bf8@windsurf>
Date: Fri, 21 Feb 2025 09:46:13 +0100
From: Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, "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>, "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 Thu, 20 Feb 2025 19:26:41 +0100
Théo Lebrun <theo.lebrun@...tlin.com> wrote:

> That used to exist! I cannot see how it could be a good idea to
> reintroduce the distinction though.
> 
> commit eca3930163ba8884060ce9d9ff5ef0d9b7c7b00f
> Author: Grant Likely <grant.likely@...retlab.ca>
> Date:   Tue Jun 8 07:48:21 2010 -0600
> 
>     of: Merge of_platform_bus_type with platform_bus_type

I don't really see how an of_platform bus would make sense. OF is not a
bus at all, it's a way of providing HW description to an operating
system.

What would IMO make a lot more sense is mmio_bus, for Memory-Mapped I/O
peripherals. mmio_device can be described through OF, through old-style
board.c, possibly through ACPI, or other means.

But in my eyes, the current platform bus is exactly this: the bus for
MMIO devices. It would have be clearer to name it mmio_bus, and that
would have probably prevented abuses of the platform bus for things
that aren't memory-mapped peripherals.

But clearly any bus that has "OF" in its name is wrong, as OF cannot be
a bus. Keep in mind that OF allows to describe not only MMIO devices,
but also I2C devices, SPI devices, MMC/SDIO devices, PCI devices, USB
devices, etc. OF is a description of the HW, not a bus.

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com