linux-kernel - Re: [PATCH v2] zram: Fix the issue that the write

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20251118095821.ebea2deea23aea6921866aa8@linux-foundation.org>
Date: Tue, 18 Nov 2025 09:58:21 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Yuwen Chen <ywen.chen@...mail.com>
Cc: senozhatsky@...omium.org, bgeffon@...gle.com, licayy@...look.com,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, minchan@...nel.org, richardycc@...gle.com
Subject: Re: [PATCH v2] zram: Fix the issue that the write - back limits
 might overflow

On Tue, 18 Nov 2025 16:15:50 +0800 Yuwen Chen <ywen.chen@...mail.com> wrote:

> Since the value of bd_wb_limit is an unsigned number, when the
> page size is larger than 4 KB, it may cause an out-of-bounds situation.

Please update the changelog to fully describe this out-of-bounds
situation.  Where does it occur, why, how, with what effects?

> This patch fixes the issue by limiting bd_wb_limit to be an
> integer multiple of PAGE_SIZE / 4096.

I don't see at all how clearing the lower 11 bits is related to "page
size is larger than 4 KB".

All quite confusing!

> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -579,6 +579,7 @@ static ssize_t writeback_limit_store(struct device *dev,
>  	if (kstrtoull(buf, 10, &val))
>  		return ret;
>  
> +	val = val & (~((1UL << (PAGE_SHIFT - 12)) - 1));

Needs a little comment, I suggest.

>  	down_write(&zram->init_lock);
>  	zram->bd_wb_limit = val;
>  	up_write(&zram->init_lock);
> -- 
> 2.34.1