Commit 86c908b4 authored by Eric Dumazet's avatar Eric Dumazet Committed by Luis Henriques

net: fix a race in dst_release()

commit d69bbf88 upstream.

Only cpu seeing dst refcount going to 0 can safely
dereference dst->flags.

Otherwise an other cpu might already have freed the dst.

Fixes: 27b75c95 ("net: avoid RCU for NOCACHE dst")
Reported-by: default avatarGreg Thelen <gthelen@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 299b6c90
...@@ -285,7 +285,7 @@ void dst_release(struct dst_entry *dst) ...@@ -285,7 +285,7 @@ void dst_release(struct dst_entry *dst)
newrefcnt = atomic_dec_return(&dst->__refcnt); newrefcnt = atomic_dec_return(&dst->__refcnt);
WARN_ON(newrefcnt < 0); WARN_ON(newrefcnt < 0);
if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE))
call_rcu(&dst->rcu_head, dst_destroy_rcu); call_rcu(&dst->rcu_head, dst_destroy_rcu);
} }
} }
......
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