net: fix a race in dst_release()
Only cpu seeing dst refcount going to 0 can safely
dereference dst->flags.
Otherwise an other cpu might already have freed the dst.
Fixes: 27b75c95f10d ("net: avoid RCU for NOCACHE dst")
Reported-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dst.c b/net/core/dst.c
index 2a18180..e6dc772 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -306,7 +306,7 @@
if (unlikely(newrefcnt < 0))
net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
__func__, dst, newrefcnt);
- if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt)
+ if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE))
call_rcu(&dst->rcu_head, dst_destroy_rcu);
}
}