Commit 07a5d384 authored Jan 06, 2016 by Francesco Ruggeri Committed by David S. Miller Jan 06, 2016

net: possible use after free in dst_release



dst_release should not access dst->flags after decrementing
__refcnt to 0. The dst_entry may be in dst_busy_list and
dst_gc_task may dst_destroy it before dst_release gets a chance
to access dst->flags.

Fixes: d69bbf88 ("net: fix a race in dst_release()")
Fixes: 27b75c95 ("net: avoid RCU for NOCACHE dst")
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 73c20a8b

net/core/dst.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -301,12 +301,13 @@ void dst_release(struct dst_entry *dst)
		{
		if (dst) {
		int newrefcnt;
		unsigned short nocache = dst->flags & DST_NOCACHE;

		newrefcnt = atomic_dec_return(&dst->__refcnt);
		if (unlikely(newrefcnt < 0))
		net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
		__func__, dst, newrefcnt);
		if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE))
		if (!newrefcnt && unlikely(nocache))
		call_rcu(&dst->rcu_head, dst_destroy_rcu);
		}
		}

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