Re: [PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

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

On Tue, Jan 16, 2018 at 06:02:07PM +0000, Eremin, Dmitry wrote:
> The logic of the original commit 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
> was assumed conditional free of struct kib_conn if the second argument free_conn in function
> kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn) is true. But this hunk of code was dropped
> from original commit. As result the logic works wrong and current code use struct kib_conn after
> free.
> 
> > drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> >   3317                          kiblnd_destroy_conn(conn, !peer);
> >                                                     ^^^^ Freed always (but should be conditionally)
> >   3318
> >   3319                          spin_lock_irqsave(lock, flags);
> >   3320                          if (!peer)
> >   3321                                  continue;
> >   3322
> >   3323                          conn->ibc_peer = peer;
> >                                     ^^^^^^^^^^^^^ Use after free
> >   3324                          if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
> >   3325                                  list_add_tail(&conn->ibc_list,
> >                                                                        ^^^^^^^^^^^^
> >   3326                                                &kiblnd_data.kib_reconn_list);
> >   3327                          else
> >   3328                                  list_add_tail(&conn->ibc_list,
> >                                                                         ^^^^^^^^^^^^
> >   3329                                                &kiblnd_data.kib_reconn_wait);
> 
> After attached patch this code will use struct kib_conn only when it was not freed.
> 
> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
> ---
>  drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> index 2ebc484..a15a625 100644
> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> @@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
>  		atomic_dec(&net->ibn_nconns);
>  	}
>  
> -	kfree(conn);
> +	if (free_conn)
> +		kfree(conn);
>  }
>  
>  int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)

This patch needs a real "Fixes:" tag, right?

Also, as this was from 4.6, it should go to the stable trees, right?
Can you resend this with that info, and then send a follow-on patch to
fix this up the way I recommended so that no one is confused in the
future?

thanks,

greg k-h