From 96e97bc07e90f175a8980a22827faf702ca4cb30 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 26 Aug 2020 12:40:06 -0700 Subject: net: disable netpoll on fresh napis 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 Fixes: 2d8bff12699a ("netpoll: Close race condition between poll_one_napi and napi_disable") Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller --- net/core/netpoll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/core/netpoll.c') diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 093e90e52bc2..2338753e936b 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -162,7 +162,7 @@ static void poll_napi(struct net_device *dev) struct napi_struct *napi; int cpu = smp_processor_id(); - list_for_each_entry(napi, &dev->napi_list, dev_list) { + list_for_each_entry_rcu(napi, &dev->napi_list, dev_list) { if (cmpxchg(&napi->poll_owner, -1, cpu) == -1) { poll_one_napi(napi); smp_store_release(&napi->poll_owner, -1); -- cgit v1.2.3-59-g8ed1b