Re: [PATCH] net_sched: reset pointers to tcf blocks in classful qdiscs' destructors

From: Konstantin Khlebnikov <redacted>
Date: Tue, 15 Aug 2017 16:35:21 +0300

Traffic filters could keep direct pointers to classes in classful qdisc,
thus qdisc destruction first removes all filters before freeing classes.
Class destruction methods also tries to free attached filters but now
this isn't safe because tcf_block_put() unlike to tcf_destroy_chain()
cannot be called second time.

This patch set class->block to NULL after first tcf_block_put() and
turn second call into no-op.

Signed-off-by: Konstantin Khlebnikov <redacted>
Fixes: 6529eaba33f0 ("net: sched: introduce tcf block infractructure")

Applied and queued up for -stable.