From 3d210534cc93dab39a9d1a8d674aa2872c268d38 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Sat, 16 Feb 2019 10:58:26 -0800 Subject: [PATCH] net_sched: fix a race condition in tcindex_destroy() (cherry picked from commit 8015d93ebd27484418d4952284fd02172fa4b0b2) tcindex_destroy() invokes tcindex_destroy_element() via a walker to delete each filter result in its perfect hash table, and tcindex_destroy_element() calls tcindex_delete() which schedules tcf RCU works to do the final deletion work. Unfortunately this races with the RCU callback __tcindex_destroy(), which could lead to use-after-free as reported by Adrian. Fix this by migrating this RCU callback to tcf RCU work too, as that workqueue is ordered, we will not have use-after-free. Note, we don't need to hold netns refcnt because we don't call tcf_exts_destroy() here. Fixes: 27ce4f05e2ab ("net_sched: use tcf_queue_work() in tcindex filter") Reported-by: Adrian Cc: Ben Hutchings Cc: Jamal Hadi Salim Cc: Jiri Pirko Signed-off-by: Cong Wang Signed-off-by: David S. Miller --- net/sched/cls_tcindex.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c index e1981628047b..81a433ae31b3 100644 --- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -48,7 +48,7 @@ struct tcindex_data { u32 hash; /* hash table size; 0 if undefined */ u32 alloc_hash; /* allocated size */ u32 fall_through; /* 0: only classify if explicit match */ - struct rcu_head rcu; + struct rcu_work rwork; }; static inline int tcindex_filter_is_set(struct tcindex_filter_result *r) @@ -229,9 +229,11 @@ static int tcindex_destroy_element(struct tcf_proto *tp, return tcindex_delete(tp, arg, &last, false, NULL); } -static void __tcindex_destroy(struct rcu_head *head) +static void tcindex_destroy_work(struct work_struct *work) { - struct tcindex_data *p = container_of(head, struct tcindex_data, rcu); + struct tcindex_data *p = container_of(to_rcu_work(work), + struct tcindex_data, + rwork); kfree(p->perfect); kfree(p->h); @@ -258,9 +260,11 @@ static int tcindex_filter_result_init(struct tcindex_filter_result *r) return tcf_exts_init(&r->exts, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); } -static void __tcindex_partial_destroy(struct rcu_head *head) +static void tcindex_partial_destroy_work(struct work_struct *work) { - struct tcindex_data *p = container_of(head, struct tcindex_data, rcu); + struct tcindex_data *p = container_of(to_rcu_work(work), + struct tcindex_data, + rwork); kfree(p->perfect); kfree(p); @@ -480,7 +484,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, } if (oldp) - call_rcu(&oldp->rcu, __tcindex_partial_destroy); + tcf_queue_work(&oldp->rwork, tcindex_partial_destroy_work); return 0; errout_alloc: @@ -572,7 +576,7 @@ static void tcindex_destroy(struct tcf_proto *tp, bool rtnl_held, walker.fn = tcindex_destroy_element; tcindex_walk(tp, &walker, true); - call_rcu(&p->rcu, __tcindex_destroy); + tcf_queue_work(&p->rwork, tcindex_destroy_work); } -- 2.39.5