From c5b68284bce51609dd38d4422f7544a5cd8da200 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Tue, 22 Sep 2020 10:14:03 +0800 Subject: [PATCH] net_sched: cls_route: remove the right filter from hashtable stable inclusion from linux-4.19.114 commit ea3d6652c240978736a91b9e85fde9fee9359be4 -------------------------------- [ Upstream commit ef299cc3fa1a9e1288665a9fdc8bff55629fd359 ] 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 Cc: Jiri Pirko Cc: John Fastabend Signed-off-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang Signed-off-by: Li Aichun Reviewed-by: guodeqing Signed-off-by: Yang Yingliang --- net/sched/cls_route.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c index 0404aa5fa7cb..0a0a22a0666d 100644 --- a/net/sched/cls_route.c +++ b/net/sched/cls_route.c @@ -536,8 +536,8 @@ 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; } } -- GitLab