netdev - Re: [net 1/1] tipc: fix use-after-free in tipc_nametbl

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Message-Id: <20180418.134858.507740622493599561.davem@davemloft.net>
Date:   Wed, 18 Apr 2018 13:48:58 -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 use-after-free in tipc_nametbl_stop

From: Jon Maloy <jon.maloy@...csson.com>
Date: Tue, 17 Apr 2018 21:25:42 +0200

> When we delete a service item in tipc_nametbl_stop() we loop over
> all service ranges in the service's RB tree, and for each service
> range we loop over its pertaining publications while calling
> tipc_service_remove_publ() for each of them.
> 
> However, tipc_service_remove_publ() has the side effect that it also
> removes the comprising service range item when there are no publications
> left. This leads to a "use-after-free" access when the inner loop
> continues to the next iteration, since the range item holding the list
> we are looping no longer exists.
> 
> We fix this by moving the delete of the service range item outside
> the said function. Instead, we now let the two functions calling it
> test if the list is empty and perform the removal when that is the
> case.
> 
> Reported-by: syzbot+d64b64afc55660106556@...kaller.appspotmail.com
> Signed-off-by: Jon Maloy <jon.maloy@...csson.com>

Applied.