From b1be2e8cd290f620777bfdb8aa00890cd2fa02b5 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Wed, 11 Mar 2020 22:42:27 -0700 Subject: [PATCH] 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. Reported-and-tested-by: syzbot+653090db2562495901dc@syzkaller.appspotmail.com 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 --- net/sched/cls_tcindex.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c index 09b7dc5fe7e0..f2cb24b6f0cf 100644 --- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -261,8 +261,10 @@ static void tcindex_partial_destroy_work(struct work_struct *work) struct tcindex_data, rwork); + rtnl_lock(); kfree(p->perfect); kfree(p); + rtnl_unlock(); } static void tcindex_free_perfect_hash(struct tcindex_data *cp)