Re: [PATCH] mm: cleancache: fix potential race in cleancache apis

[gregkh@xxxxxxxxxxxxxxxxxxx]

On Wed, Jun 30, 2021 at 04:33:10PM +0900, 권오훈 wrote:
> Current cleancache api implementation has potential race as follows,
> which might lead to corruption in filesystems using cleancache.
> 
> thread 0                thread 1                        thread 2
> 
>                         in put_page
>                         get pool_id K for fs1
> invalidate_fs on fs1
> frees pool_id K
>                                                         init_fs for fs2
>                                                         allocates pool_id K
>                         put_page puts page
>                         which belongs to fs1
>                         into cleancache pool for fs2
> 
> At this point, a file cache which originally belongs to fs1 might be
> copied back to cleancache pool of fs2, which might be later used as if
> it were normal cleancache of fs2, and could eventually corrupt fs2 when
> flushed back.
> 
> Add rwlock in order to synchronize invalidate_fs with other cleancache
> operations.
> 
> In normal situations where filesystems are not frequently mounted or
> unmounted, there will be little performance impact since
> read_lock/read_unlock apis are used.
> 
> Signed-off-by: Ohhoon Kwon <ohoono.kwon@xxxxxxxxxxx>

What commit does this fix?  Should it go to stable kernels?

thanks,

greg k-h