Commit a35165ca authored Sep 22, 2014 by Eric Dumazet Committed by David S. Miller Sep 22, 2014

ipv4: do not use this_cpu_ptr() in preemptible context

this_cpu_ptr() in preemptible context is generally bad

Sep 22 05:05:55 br kernel: [   94.608310] BUG: using smp_processor_id()
in
preemptible [00000000] code: ip/2261
Sep 22 05:05:55 br kernel: [   94.608316] caller is
tunnel_dst_set.isra.28+0x20/0x60 [ip_tunnel]
Sep 22 05:05:55 br kernel: [   94.608319] CPU: 3 PID: 2261 Comm: ip Not
tainted
3.17.0-rc5 #82

We can simply use raw_cpu_ptr(), as preemption is safe in these
contexts.

Should fix https://bugzilla.kernel.org/show_bug.cgi?id=84991



Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Joe <joe9mail@gmail.com>
Fixes: 9a4aa9af ("ipv4: Use percpu Cache route in IP tunnels")
Acked-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 84de67b2

net/ipv4/ip_tunnel.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -79,10 +79,10 @@ static void __tunnel_dst_set(struct ip_tunnel_dst *idst,
		idst->saddr = saddr;
		}

		static void tunnel_dst_set(struct ip_tunnel *t,
		static noinline void tunnel_dst_set(struct ip_tunnel *t,
		struct dst_entry *dst, __be32 saddr)
		{
		__tunnel_dst_set(this_cpu_ptr(t->dst_cache), dst, saddr);
		__tunnel_dst_set(raw_cpu_ptr(t->dst_cache), dst, saddr);
		}

		static void tunnel_dst_reset(struct ip_tunnel *t)
		@@ -106,7 +106,7 @@ static struct rtable tunnel_rtable_get(struct ip_tunnel t,
		struct dst_entry *dst;

		rcu_read_lock();
		idst = this_cpu_ptr(t->dst_cache);
		idst = raw_cpu_ptr(t->dst_cache);
		dst = rcu_dereference(idst->dst);
		if (dst && !atomic_inc_not_zero(&dst->__refcnt))
		dst = NULL;

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