This is a note to let you know that I've just added the patch titled bnxt: don't enable NAPI until rings are ready to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bnxt-don-t-enable-napi-until-rings-are-ready.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 96ecdcc992eb7f468b2cf829b0f5408a1fad4668 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski <kuba@xxxxxxxxxx> Date: Wed, 26 Aug 2020 12:40:07 -0700 Subject: bnxt: don't enable NAPI until rings are ready From: Jakub Kicinski <kuba@xxxxxxxxxx> commit 96ecdcc992eb7f468b2cf829b0f5408a1fad4668 upstream. 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 <rsher@xxxxxx> Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.") Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Reviewed-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 | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c @@ -4612,14 +4612,14 @@ static int __bnxt_open_nic(struct bnxt * } } - bnxt_enable_napi(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); + if (link_re_init) { rc = bnxt_update_phy_setting(bp); if (rc) @@ -4644,9 +4644,6 @@ static int __bnxt_open_nic(struct bnxt * return 0; -open_err: - bnxt_disable_napi(bp); - open_err_irq: bnxt_del_napi(bp); Patches currently in stable-queue which might be from kuba@xxxxxxxxxx are queue-4.4/bnxt-don-t-enable-napi-until-rings-are-ready.patch queue-4.4/net-disable-netpoll-on-fresh-napis.patch