netdev - [PATCH net-next 21/21] net: add debug atomic_inc_not_zero() in dst

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Date:   Fri, 16 Jun 2017 10:47:44 -0700
From:   Wei Wang <tracywwnj@...il.com>
To:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Martin KaFai Lau <kafai@...com>, Wei Wang <weiwan@...gle.com>
Subject: [PATCH net-next 21/21] net: add debug atomic_inc_not_zero() in dst_hold()

From: Wei Wang <weiwan@...gle.com>

This patch is meant to add a debug warning on the situation where dst is
being held during its destroy phase. This could potentially cause double
free issue on the dst.

Signed-off-by: Wei Wang <weiwan@...gle.com>
Acked-by: Martin KaFai Lau <kafai@...com>
---
 include/net/dst.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/dst.h b/include/net/dst.h
index d912b44d2dcb..f73611ec4017 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -251,7 +251,7 @@ static inline void dst_hold(struct dst_entry *dst)
 	 * __pad_to_align_refcnt declaration in struct dst_entry
 	 */
 	BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
-	atomic_inc(&dst->__refcnt);
+	WARN_ON(atomic_inc_not_zero(&dst->__refcnt) == 0);
 }
 
 static inline void dst_use(struct dst_entry *dst, unsigned long time)
-- 
2.13.1.518.g3df882009-goog