From: Eric Dumazet <eduma...@google.com>

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 <gthe...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
---
 net/core/dst.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dst.c b/net/core/dst.c
index 2a1818065e12..e6dc77252fe9 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -306,7 +306,7 @@ void dst_release(struct dst_entry *dst)
                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);
        }
 }


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