| Message ID | 20200314052954.26885-1-xiyou.wangcong@gmail.com |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] net_sched: cls_route: remove the right filter from hashtable | expand |
From: Cong Wang <xiyou.wangcong@gmail.com> Date: Fri, 13 Mar 2020 22:29:54 -0700 > route4_change() allocates a new filter and copies values from > the old one. After the new filter is inserted into the hash > table, the old filter should be removed and freed, as the final > step of the update. > > However, the current code mistakenly removes the new one. This > looks apparently wrong to me, and it causes double "free" and > use-after-free too, as reported by syzbot. > > Reported-and-tested-by: syzbot+f9b32aaacd60305d9687@syzkaller.appspotmail.com > Reported-and-tested-by: syzbot+2f8c233f131943d6056d@syzkaller.appspotmail.com > Reported-and-tested-by: syzbot+9c2df9fd5e9445b74e01@syzkaller.appspotmail.com > Fixes: 1109c00547fc ("net: sched: RCU cls_route") > Cc: Jamal Hadi Salim <jhs@mojatatu.com> > Cc: Jiri Pirko <jiri@resnulli.us> > Cc: John Fastabend <john.fastabend@gmail.com> > Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Applied and queued up for -stable, thanks Cong.
diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c index 6f8786b06bde..5efa3e7ace15 100644 --- a/net/sched/cls_route.c +++ b/net/sched/cls_route.c @@ -534,8 +534,8 @@ static int route4_change(struct net *net, struct sk_buff *in_skb, fp = &b->ht[h]; for (pfp = rtnl_dereference(*fp); pfp; fp = &pfp->next, pfp = rtnl_dereference(*fp)) { - if (pfp == f) { - *fp = f->next; + if (pfp == fold) { + rcu_assign_pointer(*fp, fold->next); break; } }
route4_change() allocates a new filter and copies values from the old one. After the new filter is inserted into the hash table, the old filter should be removed and freed, as the final step of the update. However, the current code mistakenly removes the new one. This looks apparently wrong to me, and it causes double "free" and use-after-free too, as reported by syzbot. Reported-and-tested-by: syzbot+f9b32aaacd60305d9687@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+2f8c233f131943d6056d@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+9c2df9fd5e9445b74e01@syzkaller.appspotmail.com Fixes: 1109c00547fc ("net: sched: RCU cls_route") Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Jiri Pirko <jiri@resnulli.us> Cc: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> --- net/sched/cls_route.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)