From c3317f4db831b7564ff8d1670326456a7fbbbcb3 Mon Sep 17 00:00:00 2001 From: Jon Maloy Date: Wed, 11 Apr 2018 22:52:09 +0200 Subject: tipc: fix unbalanced reference counter When a topology subscription is created, we may encounter (or KASAN may provoke) a failure to create a corresponding service instance in the binding table. Instead of letting the tipc_nametbl_subscribe() report the failure back to the caller, the function just makes a warning printout and returns, without incrementing the subscription reference counter as expected by the caller. This makes the caller believe that the subscription was successful, so it will at a later moment try to unsubscribe the item. This involves a sub_put() call. Since the reference counter never was incremented in the first place, we get a premature delete of the subscription item, followed by a "use-after-free" warning. We fix this by adding a return value to tipc_nametbl_subscribe() and make the caller aware of the failure to subscribe. This bug seems to always have been around, but this fix only applies back to the commit shown below. Given the low risk of this happening we believe this to be sufficient. Fixes: commit 218527fe27ad ("tipc: replace name table service range array with rb tree") Reported-by: syzbot+aa245f26d42b8305d157@syzkaller.appspotmail.com Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/subscr.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'net/tipc/subscr.c') diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c index b7d80bc5f4ab..f340e53da625 100644 --- a/net/tipc/subscr.c +++ b/net/tipc/subscr.c @@ -153,7 +153,10 @@ struct tipc_subscription *tipc_sub_subscribe(struct net *net, memcpy(&sub->evt.s, s, sizeof(*s)); spin_lock_init(&sub->lock); kref_init(&sub->kref); - tipc_nametbl_subscribe(sub); + if (!tipc_nametbl_subscribe(sub)) { + kfree(sub); + return NULL; + } timer_setup(&sub->timer, tipc_sub_timeout, 0); timeout = tipc_sub_read(&sub->evt.s, timeout); if (timeout != TIPC_WAIT_FOREVER) -- cgit v1.2.3