Re: [B.A.T.M.A.N.] [PATCH maint v2] batman-adv: Reduce refcnt of removed router when updating route

[Marek Lindner <mareklindner@neomailbox.ch>]

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On Sunday, March 20, 2016 12:27:53 Sven Eckelmann wrote:
> _batadv_update_route rcu_derefences orig_ifinfo->router outside of a
> spinlock protected region to print some information messages to the debug
> log. But this pointer is not checked again when the new pointer is assigned
> in the spinlock protected region. Thus is can happen that the value of
> orig_ifinfo->router changed in the meantime and thus the reference counter
> of the wrong router gets reduced after the spinlock protected region.
> 
> Just rcu_dereferencing the value of orig_ifinfo->router inside the spinlock
> protected region (which also set the new pointer) is enough to get the
> correct old router object.
> 
> Fixes: d90ddb94423f ("batman-adv: Make orig_node->router an rcu protected
> pointer") Signed-off-by: Sven Eckelmann <sven@narfation.org>
> --
> v2:
>  - add comment explaining the idea behind the extra
> rcu_dereference_protected ---
>  net/batman-adv/routing.c | 7 +++++++
>  1 file changed, 7 insertions(+)

Applied with minor modifications in revision 08ba64d.

Thanks,
Marek

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