batman-adv: Reduce refcnt of removed router when updating route

batman-adv: Reduce refcnt of removed router when updating route

Orabug: 25308073

[ Upstream commit d1a65f1741bfd9c69f9e4e2ad447a89b6810427d ]

_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: e1a5382f978b ("batman-adv: Make orig_node->router an rcu protected pointer")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit b55c212a0f25d8999b9601a120506861d85f6fd3)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>