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SubjectRE: [PATCH] lan78xx: Connect phy early
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Hi Alexander,

Thanks for patch. We will look into it if there is any corner case
Such as plug in/out while operations.

Woojung

> -----Original Message-----
> From: Alexander Graf [mailto:agraf@suse.de]
> Sent: Wednesday, March 14, 2018 10:55 AM
> To: Woojung Huh - C21699 <Woojung.Huh@microchip.com>
> Cc: UNGLinuxDriver <UNGLinuxDriver@microchip.com>; netdev@vger.kernel.org; linux-
> usb@vger.kernel.org; linux-kernel@vger.kernel.org; Thomas Bogendoerfer
> <tbogendoerfer@suse.de>; Phil Elwell <phil@raspberrypi.org>
> Subject: [PATCH] lan78xx: Connect phy early
>
> When using wicked with a lan78xx device attached to the system, we
> end up with ethtool commands issued on the device before an ifup
> got issued. That lead to the following crash:
>
> Unable to handle kernel NULL pointer dereference at virtual address 0000039c
> pgd = ffff800035b30000
> [0000039c] *pgd=0000000000000000
> Internal error: Oops: 96000004 [#1] SMP
> Modules linked in: [...]
> Supported: Yes
> CPU: 3 PID: 638 Comm: wickedd Tainted: G E 4.12.14-0-default #1
> Hardware name: raspberrypi rpi/rpi, BIOS 2018.03-rc2 02/21/2018
> task: ffff800035e74180 task.stack: ffff800036718000
> PC is at phy_ethtool_ksettings_get+0x20/0x98
> LR is at lan78xx_get_link_ksettings+0x44/0x60 [lan78xx]
> pc : [<ffff0000086f7f30>] lr : [<ffff000000dcca84>] pstate: 20000005
> sp : ffff80003671bb20
> x29: ffff80003671bb20 x28: ffff800035e74180
> x27: ffff000008912000 x26: 000000000000001d
> x25: 0000000000000124 x24: ffff000008f74d00
> x23: 0000004000114809 x22: 0000000000000000
> x21: ffff80003671bbd0 x20: 0000000000000000
> x19: ffff80003671bbd0 x18: 000000000000040d
> x17: 0000000000000001 x16: 0000000000000000
> x15: 0000000000000000 x14: ffffffffffffffff
> x13: 0000000000000000 x12: 0000000000000020
> x11: 0101010101010101 x10: fefefefefefefeff
> x9 : 7f7f7f7f7f7f7f7f x8 : fefefeff31677364
> x7 : 0000000080808080 x6 : ffff80003671bc9c
> x5 : ffff80003671b9f8 x4 : ffff80002c296190
> x3 : 0000000000000000 x2 : 0000000000000000
> x1 : ffff80003671bbd0 x0 : ffff80003671bc00
> Process wickedd (pid: 638, stack limit = 0xffff800036718000)
> Call trace:
> Exception stack(0xffff80003671b9e0 to 0xffff80003671bb20)
> b9e0: ffff80003671bc00 ffff80003671bbd0 0000000000000000 0000000000000000
> ba00: ffff80002c296190 ffff80003671b9f8 ffff80003671bc9c 0000000080808080
> ba20: fefefeff31677364 7f7f7f7f7f7f7f7f fefefefefefefeff 0101010101010101
> ba40: 0000000000000020 0000000000000000 ffffffffffffffff 0000000000000000
> ba60: 0000000000000000 0000000000000001 000000000000040d ffff80003671bbd0
> ba80: 0000000000000000 ffff80003671bbd0 0000000000000000 0000004000114809
> baa0: ffff000008f74d00 0000000000000124 000000000000001d ffff000008912000
> bac0: ffff800035e74180 ffff80003671bb20 ffff000000dcca84 ffff80003671bb20
> bae0: ffff0000086f7f30 0000000020000005 ffff80002c296000 ffff800035223900
> bb00: 0000ffffffffffff 0000000000000000 ffff80003671bb20 ffff0000086f7f30
> [<ffff0000086f7f30>] phy_ethtool_ksettings_get+0x20/0x98
> [<ffff000000dcca84>] lan78xx_get_link_ksettings+0x44/0x60 [lan78xx]
> [<ffff0000087cbc40>] ethtool_get_settings+0x68/0x210
> [<ffff0000087cc0d4>] dev_ethtool+0x214/0x2180
> [<ffff0000087e5008>] dev_ioctl+0x400/0x630
> [<ffff00000879dd00>] sock_do_ioctl+0x70/0x88
> [<ffff00000879f5f8>] sock_ioctl+0x208/0x368
> [<ffff0000082cde10>] do_vfs_ioctl+0xb0/0x848
> [<ffff0000082ce634>] SyS_ioctl+0x8c/0xa8
> Exception stack(0xffff80003671bec0 to 0xffff80003671c000)
> bec0: 0000000000000009 0000000000008946 0000fffff4e841d0 0000aa0032687465
> bee0: 0000aaaafa2319d4 0000fffff4e841d4 0000000032687465 0000000032687465
> bf00: 000000000000001d 7f7fff7f7f7f7f7f 72606b622e71ff4c 7f7f7f7f7f7f7f7f
> bf20: 0101010101010101 0000000000000020 ffffffffffffffff 0000ffff7f510c68
> bf40: 0000ffff7f6a9d18 0000ffff7f44ce30 000000000000040d 0000ffff7f6f98f0
> bf60: 0000fffff4e842c0 0000000000000001 0000aaaafa2c2e00 0000ffff7f6ab000
> bf80: 0000fffff4e842c0 0000ffff7f62a000 0000aaaafa2b9f20 0000aaaafa2c2e00
> bfa0: 0000fffff4e84818 0000fffff4e841a0 0000ffff7f5ad0cc 0000fffff4e841a0
> bfc0: 0000ffff7f44ce3c 0000000080000000 0000000000000009 000000000000001d
> bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>
> The culprit is quite simple: The driver tries to access the phy left and right,
> but only actually has a working reference to it when the device is up.
>
> The fix thus is quite simple too: Get a reference to the phy on probe already
> and keep it even when the device is going down.
>
> With this patch applied, I can successfully run wicked on my system and bring
> the interface up and down as many times as I want, without getting NULL pointer
> dereferences in between.
>
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
> drivers/net/usb/lan78xx.c | 21 ++++++++++-----------
> 1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
> index 60a604cc7647..931cc124ab0c 100644
> --- a/drivers/net/usb/lan78xx.c
> +++ b/drivers/net/usb/lan78xx.c
> @@ -2082,8 +2082,6 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
>
> dev->fc_autoneg = phydev->autoneg;
>
> - phy_start(phydev);
> -
> netif_dbg(dev, ifup, dev->net, "phy initialised successfully");
>
> return 0;
> @@ -2512,9 +2510,7 @@ static int lan78xx_open(struct net_device *net)
> if (ret < 0)
> goto done;
>
> - ret = lan78xx_phy_init(dev);
> - if (ret < 0)
> - goto done;
> + phy_start(net->phydev);
>
> /* for Link Check */
> if (dev->urb_intr) {
> @@ -2575,13 +2571,7 @@ static int lan78xx_stop(struct net_device *net)
> if (timer_pending(&dev->stat_monitor))
> del_timer_sync(&dev->stat_monitor);
>
> - phy_unregister_fixup_for_uid(PHY_KSZ9031RNX, 0xfffffff0);
> - phy_unregister_fixup_for_uid(PHY_LAN8835, 0xfffffff0);
> -
> phy_stop(net->phydev);
> - phy_disconnect(net->phydev);
> -
> - net->phydev = NULL;
>
> clear_bit(EVENT_DEV_OPEN, &dev->flags);
> netif_stop_queue(net);
> @@ -3481,6 +3471,11 @@ static void lan78xx_disconnect(struct usb_interface *intf)
> net = dev->net;
> unregister_netdev(net);
>
> + phy_unregister_fixup_for_uid(PHY_KSZ9031RNX, 0xfffffff0);
> + phy_unregister_fixup_for_uid(PHY_LAN8835, 0xfffffff0);
> +
> + phy_disconnect(net->phydev);
> +
> cancel_delayed_work_sync(&dev->wq);
>
> usb_scuttle_anchored_urbs(&dev->deferred);
> @@ -3634,6 +3629,10 @@ static int lan78xx_probe(struct usb_interface *intf,
> pm_runtime_set_autosuspend_delay(&udev->dev,
> DEFAULT_AUTOSUSPEND_DELAY);
>
> + ret = lan78xx_phy_init(dev);
> + if (ret < 0)
> + return ret;
> +
> return 0;
>
> out3:
> --
> 2.12.3

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