netdev - [PATCH net] : add a missing rcu synchronization

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Message-ID: <1479306712.8455.185.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 16 Nov 2016 06:31:52 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Michael Chan <michael.chan@...adcom.com>
Subject: [PATCH net] : add a missing rcu synchronization

From: Eric Dumazet <edumazet@...gle.com>

Add a missing synchronize_net() call to avoid potential use after free,
since we explicitly call napi_hash_del() to factorize the RCU grace
period.

Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Michael Chan <michael.chan@...adcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index c6909660e097..e18635b2a002 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -4934,6 +4934,10 @@ static void bnxt_del_napi(struct bnxt *bp)
 		napi_hash_del(&bnapi->napi);
 		netif_napi_del(&bnapi->napi);
 	}
+	/* We called napi_hash_del() before netif_napi_del(), we need
+	 * to respect an RCU grace period before freeing napi structures.
+	 */
+	synchronize_net();
 }
 
 static void bnxt_init_napi(struct bnxt *bp)