linux-kernel - Re: Re: [PATCH] ext4: Fix KASAN use-after-free in ext4_find

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Message-ID: <2ef68a02.45e3e.19b2ce7b7a0.Coremail.3230100410@zju.edu.cn>
Date: Wed, 17 Dec 2025 23:22:21 +0800 (GMT+08:00)
From: 余昊铖 <3230100410@....edu.cn>
To: "Baokun Li" <libaokun1@...wei.com>
Cc: security@...nel.org, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH] ext4: Fix KASAN use-after-free in ext4_find_extent

Hi,

Sorry but I am a bit confused by your words. My original fuzz tesing already enabled CONFIG_BLK_DEV_WRITE_MOUNTED as in most major Linux distributions. 

So does a bug found when CONFIG_BLK_DEV_WRITE_MOUNTED is enabled still hold value for reporting? Should I enable or disable this configuration in my future fuzzing work?

Thanks,
Haocheng Yu

> > Hi,
> >
> > I have disabled CONFIG_BLK_DEV_WRITE_MOUNTED and spent some time trying to trigger the reported KASAN issues. And I found neither of the two bugs has been observed since. Is this issue still worth investigating?
> 
> That essentially confirms the issue is caused by bypassing the
> filesystem to write directly to the raw disk. This is a known
> issue and is quite tricky to solve.
> 
> You can work around this specific class of issues in your fuzz
> testing by enabling CONFIG_BLK_DEV_WRITE_MOUNTED. Syzbot runs
> with this configuration enabled by default.
> 
> 
> Cheers,
> Baokun