Re: [PATCH 6.1.y] btrfs: fix extent map use-after-free when adding pages to compressed bio

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Aug 30, 2024 at 03:45:36PM -0700, Brennan Lamoreaux wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> commit 8e7860543a94784d744c7ce34b78a2e11beefa5c upstream.
> 
> At add_ra_bio_pages() we are accessing the extent map to calculate
> 'add_size' after we dropped our reference on the extent map, resulting
> in a use-after-free. Fix this by computing 'add_size' before dropping our
> extent map reference.
> 
> Reported-by: syzbot+853d80cba98ce1157ae6@syzkaller.appspotmail.com
> Link: https://lore.kernel.org/linux-btrfs/000000000000038144061c6d18f2@google.com/
> Fixes: 6a4049102055 ("btrfs: subpage: make add_ra_bio_pages() compatible")
> CC: stable@vger.kernel.org # 6.1+
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> Reviewed-by: David Sterba <dsterba@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> [ Brennan: Applied to v6.1 ]
> Signed-off-by: Brennan Lamoreaux <brennan.lamoreaux@broadcom.com>
> ---
>  fs/btrfs/compression.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Now queued up, thanks.

greg k-h