linux-kernel - Re: CVE-2025-40128: btrfs: fix symbolic link reading when bs

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Message-ID: <2025111342-maroon-untouched-02a8@gregkh>
Date: Thu, 13 Nov 2025 12:37:53 -0500
From: Greg Kroah-Hartman <gregkh@...nel.org>
To: David Sterba <dsterba@...e.cz>
Cc: cve@...nel.org, linux-kernel@...r.kernel.org,
	linux-cve-announce@...r.kernel.org
Subject: Re: CVE-2025-40128: btrfs: fix symbolic link reading when bs > ps

On Thu, Nov 13, 2025 at 11:40:08AM +0100, David Sterba wrote:
> On Wed, Nov 12, 2025 at 07:24:04PM +0900, Greg Kroah-Hartman wrote:
> > From: Greg Kroah-Hartman <gregkh@...nel.org>
> > 
> > Description
> > ===========
> > 
> > In the Linux kernel, the following vulnerability has been resolved:
> > 
> > btrfs: fix symbolic link reading when bs > ps
> > 
> > [BUG DURING BS > PS TEST]
> > When running the following script on a btrfs whose block size is larger
> > than page size, e.g. 8K block size and 4K page size, it will trigger a
> > kernel BUG:
> > 
> >   # mkfs.btrfs -s 8k $dev
> >   # mount $dev $mnt
> >   # mkdir $mnt/dir
> >   # ln -s dir $mnt/link
> >   # ls $mnt/link
> 
> Please drop the CVE status from this patch, the bs > ps (block size
> bigger than page size) feature requires CONFIG_BTRFS_EXPERIMENTAL and is
> unfinished and possibly unstable in other use cases. It does not make
> sense to improve security where none should be expected.

Oops, good catch, now rejected, thanks for the review!

greg k-h