linux-kernel - Re: [PATCH v3] zram: don't free statically defined names

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Message-ID: <20240924054951.GM38742@google.com>
Date: Tue, 24 Sep 2024 14:49:51 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Andrey Skvortsov <andrej.skvortzov@...il.com>,
	Venkat Rao Bagalkote <venkat88@...ux.vnet.ibm.com>,
	Minchan Kim <minchan@...nel.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v3] zram: don't free statically defined names

On (24/09/24 07:21), Christophe JAILLET wrote:
[..]
> > kfree_const() will not work if zram is built as a module. It works
> > only for .rodata for kernel image. [1]
> > 
> > 1. https://elixir.bootlin.com/linux/v6.11/source/include/asm-generic/sections.h#L177
> > 
> 
> If so, then it is likely that it is not correctly used elsewhere.
> 
> https://elixir.bootlin.com/linux/v6.11/source/drivers/dax/kmem.c#L289
> https://elixir.bootlin.com/linux/v6.11/source/drivers/firmware/arm_scmi/bus.c#L341
> https://elixir.bootlin.com/linux/v6.11/source/drivers/input/touchscreen/chipone_icn8505.c#L379

icn8505_probe_acpi() uses kfree_const(subsys)...

subsys is returned from acpi_get_subsystem_id() which only
does
		sub = kstrdup(obj->string.pointer, GFP_KERNEL);

However, if acpi_get_subsystem_id() returns an error then
icn8505_probe_acpi() does

		subsys = "unknown";

and I suspect that kfree_const(subsys) can, in fact, explode?