linux-kernel - Re: [SECURITY] ext4: KASAN use-after-free and Oops in ext4_xattr_set

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Message-ID: <2025110632-fondue-chewer-2e20@gregkh>
Date: Thu, 6 Nov 2025 16:00:25 +0900
From: Greg KH <greg@...ah.com>
To: 章怿贺 <l1zao@....edu.cn>
Cc: security@...nel.org, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [SECURITY] ext4: KASAN use-after-free and Oops in
 ext4_xattr_set_entry with crafted ext4 image

On Wed, Nov 05, 2025 at 10:39:26PM +0800, 章怿贺 wrote:
> A local unprivileged user who can mount a crafted ext4 filesystem image and call lsetxattr() on a file inside that filesystem can trigger:

Note, if you can do this, all bets are off as has been explained many
times on this list :)

The real question is, does fsck catch this issue before mounting the
filesystem?  If not, can you send a patch to fix that?

Also, do you have a patch to fix this issue so that you get the credit
for fixing it?  As you have a reproducer, you seem to have an easy way
to test this :)

thanks,

greg k-h