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net: qmi_wwan: should hold RTNL while changing netdev type 

The notifier calls were thrown in as a last-minute fix for an
imagined "this device could be part of a bridge" problem. That
revealed a certain lack of locking.  Not to mention testing...

Avoid this splat:

RTNL: assertion failed at net/core/dev.c (1639)
CPU: 0 PID: 4293 Comm: bash Not tainted 4.4.0-rc3+ #358
Hardware name: LENOVO 2776LEG/2776LEG, BIOS 6EET55WW (3.15 ) 12/19/2011
 0000000000000000 ffff8800ad253d60 ffffffff8122f7cf ffff8800ad253d98
 ffff8800ad253d88 ffffffff813833ab 0000000000000002 ffff880230f48560
 ffff880230a12900 ffff8800ad253da0 ffffffff813833da 0000000000000002
Call Trace:
 [<ffffffff8122f7cf>] dump_stack+0x4b/0x63
 [<ffffffff813833ab>] call_netdevice_notifiers_info+0x3d/0x59
 [<ffffffff813833da>] call_netdevice_notifiers+0x13/0x15
 [<ffffffffa09be227>] raw_ip_store+0x81/0x193 [qmi_wwan]
 [<ffffffff8131e149>] dev_attr_store+0x20/0x22
 [<ffffffff811d858b>] sysfs_kf_write+0x49/0x50
 [<ffffffff811d8027>] kernfs_fop_write+0x10a/0x151
 [<ffffffff8117249a>] __vfs_write+0x26/0xa5
 [<ffffffff81085ed4>] ? percpu_down_read+0x53/0x7f
 [<ffffffff81174c9e>] ? __sb_start_write+0x5f/0xb0
 [<ffffffff81174c9e>] ? __sb_start_write+0x5f/0xb0
 [<ffffffff81172c37>] vfs_write+0xa3/0xe7
 [<ffffffff811734ad>] SyS_write+0x50/0x7e
 [<ffffffff8145c517>] entry_SYSCALL_64_fastpath+0x12/0x6f

Fixes: 32f7adf633 ("net: qmi_wwan: support "raw IP" mode")
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Bjørn Mork 2015-12-06 21:25:50 +01:00 committed by David S. Miller
parent 6633d3815c
commit 6c730080e6
1 changed files with 15 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
drivers/net/usb/qmi_wwan.c
View File

@ -16,6 +16,7 @@
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/mii.h>
#include <linux/rtnetlink.h>
#include <linux/usb.h>
#include <linux/usb/cdc.h>
#include <linux/usb/usbnet.h>
@ -92,7 +93,7 @@ static ssize_t raw_ip_store(struct device *d, struct device_attribute *attr, co
struct usbnet *dev = netdev_priv(to_net_dev(d));
struct qmi_wwan_state *info = (void *)&dev->data;
bool enable;
int err;
int ret;
if (strtobool(buf, &enable))
return -EINVAL;
@ -101,18 +102,22 @@ static ssize_t raw_ip_store(struct device *d, struct device_attribute *attr, co
if (enable == (info->flags & QMI_WWAN_FLAG_RAWIP))
return len;
if (!rtnl_trylock())
return restart_syscall();
/* we don't want to modify a running netdev */
if (netif_running(dev->net)) {
netdev_err(dev->net, "Cannot change a running device\n");
return -EBUSY;
ret = -EBUSY;
goto err;
}
/* let other drivers deny the change */
err = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE, dev->net);
err = notifier_to_errno(err);
if (err) {
ret = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE, dev->net);
ret = notifier_to_errno(ret);
if (ret) {
netdev_err(dev->net, "Type change was refused\n");
return err;
goto err;
}
if (enable)
@ -121,7 +126,10 @@ static ssize_t raw_ip_store(struct device *d, struct device_attribute *attr, co
info->flags &= ~QMI_WWAN_FLAG_RAWIP;
qmi_wwan_netdev_setup(dev->net);
call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev->net);
return len;
ret = len;
err:
rtnl_unlock();
return ret;
}
static DEVICE_ATTR_RW(raw_ip);