netlink: fix netlink_change_ngroups()
commit 6c04bb18 (netlink: use call_rcu for netlink_change_ngroups) used a somewhat convoluted and racy way to perform call_rcu(). The old block of memory is freed after a grace period, but the rcu_head used to track it is located in new block. This can clash if we call two times or more netlink_change_ngroups(), and a block is freed before another. call_rcu() called on different cpus makes no guarantee in order of callbacks. Fix this using a more standard way of handling this : Each block of memory contains its own rcu_head, so that no 'use after free' can happens. Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com> CC: Johannes Berg <johannes@sipsolutions.net> CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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