From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [net 1/1] tipc: fix unbalanced reference counter
Date: Thu, 12 Apr 2018 21:49:32 -0400 (EDT)
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From: Jon Maloy <jon.maloy@ericsson.com>
Date: Wed, 11 Apr 2018 22:52:09 +0200

> 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 <jon.maloy@ericsson.com>

Applied and queued up for -stable.