Re: [B.A.T.M.A.N.] [PATCH maint] batman-adv: fix potential TT client + orig-node memory leak

[Marek Lindner <mareklindner@neomailbox.ch>]

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On Saturday 13 December 2014 23:32:15 Linus Lüssing wrote:
> This patch fixes a potential memory leak which can occur once an
> originator times out. On timeout the according global translation table
> entry might not get purged correctly. Furthermore, the non purged TT
> entry will cause its orig-node to leak, too. Which additionally can lead
> to the new multicast optimization feature not kicking in because of a
> therefore bogus counter.

So far, I am with you ..


> In the wild with larger mesh networks we saw this leak quite regularly,
> resulting in routers to reboot or killed processes. This was because
> of a combination of two bugs: The bug fixed by commit
> "batman-adv: fix delayed foreign originator recognition" (8a2ad5204674)
> amplified this memory leak heavily. Since that commit I'd expect
> it to happen rarely, probably only in paused and resumed VMs and
> devices previously in stand-by.

This section shouldn't be part of the official commit message. It is hardly 
relevant to the reviewer how often a memleak occurs and whether or not you 
need a VM to trigger it. The provided commit id isn't valid in the Linux tree.


> The issue this patch fixes is caused by batadv_orig_node_free_rcu()
> never being called because of not yet released references to the
> orig-node. References which were supposed to be released through
> batadv_orig_node_free_rcu()->batadv_tt_global_del_orig().

Could you please provide addition insight as to which references are still 
held ? I did look around but nothing obvious jumped at me. 

Generally, it wouldn't be bad if the commit message went into deeper detail 
describing the nature of the bug instead of the middle section above to make 
it easy to understand what is being fixed.


Cheers,
Marek

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