linux-kernel - Re: [PATCH 1/2] zram: refuse to use zero sized block device as backing device

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Message-ID: <20241205070552.GE16709@google.com>
Date: Thu, 5 Dec 2024 16:05:52 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Minchan Kim <minchan@...nel.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
	Desheng Wu <deshengwu@...cent.com>, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] zram: refuse to use zero sized block device as
 backing device

On (24/12/05 02:02), Kairui Song wrote:
> From: Kairui Song <kasong@...cent.com>
> 
> Setting a zero sized block device as backing device is pointless, and
> one can easily create a recursive loop by setting the uninitialized
> ZRAM device itself as its own backing device by (zram0 is uninitialized):
> 
>     echo /dev/zram0 > /sys/block/zram0/backing_dev
> 
> It's definitely a wrong config, and the module will pin itself,
> kernel should refuse doing so in the first place.
> 
> By refusing to use zero sized device we avoided misuse cases
> including this one above.
> 
> Fixes: 013bf95a83ec ("zram: add interface to specif backing device")
> Reported-by: Desheng Wu <deshengwu@...cent.com>
> Signed-off-by: Kairui Song <kasong@...cent.com>
> Cc: stable@...r.kernel.org

Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>