netdev - Re: [net 1/1] tipc: fix unbalanced reference counter

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Message-Id: <20180412.214932.560777541908174607.davem@davemloft.net>
Date:   Thu, 12 Apr 2018 21:49:32 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     jon.maloy@...csson.com
Cc:     netdev@...r.kernel.org,
        mohan.krishna.ghanta.krishnamurthy@...csson.com,
        tung.q.nguyen@...tech.com.au, hoang.h.le@...tech.com.au,
        canh.d.luu@...tech.com.au, ying.xue@...driver.com,
        tipc-discussion@...ts.sourceforge.net
Subject: Re: [net 1/1] tipc: fix unbalanced reference counter

From: Jon Maloy <jon.maloy@...csson.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@...kaller.appspotmail.com
> 
> Signed-off-by: Jon Maloy <jon.maloy@...csson.com>

Applied and queued up for -stable.