[PATCH 4.4 272/312] bnxt: add a missing rcu synchronization

[Greg Kroah-Hartman]

From: Eric Dumazet <edumazet@xxxxxxxxxx>

commit e5f6f564fd191d365fcd775c06a732a488205588 upstream.

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@xxxxxxxxxx>
Cc: Michael Chan <michael.chan@xxxxxxxxxxxx>
Acked-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -4250,6 +4250,10 @@ static void bnxt_del_napi(struct bnxt *b
 		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)