net_sched: hold rtnl lock in tcindex_partial_destroy_work()

syzbot reported a use-after-free in tcindex_dump(). This is due to
the lack of RTNL in the deferred rcu work. We queue this work with
RTNL in tcindex_change(), later, tcindex_dump() is called:

        fh = tp->ops->get(tp, t->tcm_handle);
        err = tp->ops->change(..., &fh, ...);
        tfilter_notify(..., fh, ...);

but there is nothing to serialize the pending
tcindex_partial_destroy_work() with tcindex_dump().

Fix this by simply holding RTNL in tcindex_partial_destroy_work(),
so that it won't be called until RTNL is released after
tc_new_tfilter() is completed.

Fixes: 3d210534cc93 ("net_sched: fix a race condition in tcindex_destroy()")
Cc: Jamal Hadi Salim <>
Cc: Jiri Pirko <>
Signed-off-by: Cong Wang <>
Signed-off-by: David S. Miller <>
1 file changed