From 96e97bc07e90f175a8980a22827faf702ca4cb30 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 26 Aug 2020 12:40:06 -0700 Subject: [PATCH 1/2] 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/dev.c | 3 ++- net/core/netpoll.c | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index d42c9ea0c3c0..95ac7568f693 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6612,12 +6612,13 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi, netdev_err_once(dev, "%s() called with weight %d\n", __func__, weight); napi->weight = weight; - list_add(&napi->dev_list, &dev->napi_list); napi->dev = dev; #ifdef CONFIG_NETPOLL napi->poll_owner = -1; #endif set_bit(NAPI_STATE_SCHED, &napi->state); + set_bit(NAPI_STATE_NPSVC, &napi->state); + list_add_rcu(&napi->dev_list, &dev->napi_list); napi_hash_add(napi); } EXPORT_SYMBOL(netif_napi_add); 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); From 96ecdcc992eb7f468b2cf829b0f5408a1fad4668 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 26 Aug 2020 12:40:07 -0700 Subject: [PATCH 2/2] bnxt: don't enable NAPI until rings are ready Netpoll can try to poll napi as soon as napi_enable() is called. It crashes trying to access a doorbell which is still NULL: BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 59 PID: 6039 Comm: ethtool Kdump: loaded Tainted: G S 5.9.0-rc1-00469-g5fd99b5d9950-dirty #26 RIP: 0010:bnxt_poll+0x121/0x1c0 Code: c4 20 44 89 e0 5b 5d 41 5c 41 5d 41 5e 41 5f c3 41 8b 86 a0 01 00 00 41 23 85 18 01 00 00 49 8b 96 a8 01 00 00 0d 00 00 00 24 <89> 02 41 f6 45 77 02 74 cb 49 8b ae d8 01 00 00 31 c0 c7 44 24 1a netpoll_poll_dev+0xbd/0x1a0 __netpoll_send_skb+0x1b2/0x210 netpoll_send_udp+0x2c9/0x406 write_ext_msg+0x1d7/0x1f0 console_unlock+0x23c/0x520 vprintk_emit+0xe0/0x1d0 printk+0x58/0x6f x86_vector_activate.cold+0xf/0x46 __irq_domain_activate_irq+0x50/0x80 __irq_domain_activate_irq+0x32/0x80 __irq_domain_activate_irq+0x32/0x80 irq_domain_activate_irq+0x25/0x40 __setup_irq+0x2d2/0x700 request_threaded_irq+0xfb/0x160 __bnxt_open_nic+0x3b1/0x750 bnxt_open_nic+0x19/0x30 ethtool_set_channels+0x1ac/0x220 dev_ethtool+0x11ba/0x2240 dev_ioctl+0x1cf/0x390 sock_do_ioctl+0x95/0x130 Reported-by: Rob Sherwood Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.") Signed-off-by: Jakub Kicinski Reviewed-by: Michael Chan Signed-off-by: David S. Miller --- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c index 316227136f5b..57d0e195cddf 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c @@ -9504,15 +9504,15 @@ static int __bnxt_open_nic(struct bnxt *bp, bool irq_re_init, bool link_re_init) } } - bnxt_enable_napi(bp); - bnxt_debug_dev_init(bp); - rc = bnxt_init_nic(bp, irq_re_init); if (rc) { netdev_err(bp->dev, "bnxt_init_nic err: %x\n", rc); - goto open_err; + goto open_err_irq; } + bnxt_enable_napi(bp); + bnxt_debug_dev_init(bp); + if (link_re_init) { mutex_lock(&bp->link_lock); rc = bnxt_update_phy_setting(bp); @@ -9543,10 +9543,6 @@ static int __bnxt_open_nic(struct bnxt *bp, bool irq_re_init, bool link_re_init) bnxt_vf_reps_open(bp); return 0; -open_err: - bnxt_debug_dev_exit(bp); - bnxt_disable_napi(bp); - open_err_irq: bnxt_del_napi(bp);