net: disable netpoll on fresh napis
[ Upstream commit96e97bc07e
] napi_disable() makes sure to set the NAPI_STATE_NPSVC bit to prevent netpoll from accessing rings before init is complete. However, the same is not done for fresh napi instances in netif_napi_add(), even though we expect NAPI instances to be added as disabled. This causes crashes during driver reconfiguration (enabling XDP, changing the channel count) - if there is any printk() after netif_napi_add() but before napi_enable(). To ensure memory ordering is correct we need to use RCU accessors. Reported-by: Rob Sherwood <rsher@fb.com> Fixes:2d8bff1269
("netpoll: Close race condition between poll_one_napi and napi_disable") Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -6231,12 +6231,13 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
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netdev_err_once(dev, "%s() called with weight %d\n", __func__,
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weight);
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napi->weight = weight;
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list_add(&napi->dev_list, &dev->napi_list);
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napi->dev = dev;
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#ifdef CONFIG_NETPOLL
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napi->poll_owner = -1;
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#endif
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set_bit(NAPI_STATE_SCHED, &napi->state);
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set_bit(NAPI_STATE_NPSVC, &napi->state);
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list_add_rcu(&napi->dev_list, &dev->napi_list);
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napi_hash_add(napi);
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}
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EXPORT_SYMBOL(netif_napi_add);
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@ -161,7 +161,7 @@ static void poll_napi(struct net_device *dev)
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struct napi_struct *napi;
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int cpu = smp_processor_id();
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list_for_each_entry(napi, &dev->napi_list, dev_list) {
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list_for_each_entry_rcu(napi, &dev->napi_list, dev_list) {
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if (cmpxchg(&napi->poll_owner, -1, cpu) == -1) {
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poll_one_napi(napi);
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smp_store_release(&napi->poll_owner, -1);
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