Commit 198b12f7 authored Jun 04, 2016 by Erez Shitrit Committed by Doug Ledford Jun 07, 2016

IB/IPoIB: Fix race between ipoib_remove_one to sysfs functions



In ipoib_remove_one the driver holds the rtnl_lock and tries to do some
operation like dev_change_flags or unregister_netdev, while sysfs
callback like ipoib_vlan_delete holds sysfs mutex and tries to hold the
rtnl_lock via rtnl_trylock() and restart_syscall() if the lock is not
free, meanwhile ipoib_remove_one tries to get the sysfs lock in order to
free its sysfs directory, and we will get  a->b, b->a deadlock.

    Trace like the following:

        schedule+0x37/0x80
        schedule_preempt_disabled+0xe/0x10
        __mutex_lock_slowpath+0xb5/0x120
        mutex_lock+0x23/0x40
        rtnl_lock+0x15/0x20
        netdev_run_todo+0x17c/0x320
        rtnl_unlock+0xe/0x10
        ipoib_vlan_delete+0x11b/0x1b0 [ib_ipoib]
        delete_child+0x54/0x80 [ib_ipoib]
        dev_attr_store+0x18/0x30
        sysfs_kf_write+0x37/0x40
        mutex_lock+0x16/0x40
        SyS_write+0x55/0xc0
        entry_SYSCALL_64_fastpath+0x16/0x75
    And
        schedule+0x37/0x80
        __kernfs_remove+0x1a8/0x260
        ? wake_atomic_t_function+0x60/0x60
        kernfs_remove+0x25/0x40
        sysfs_remove_dir+0x50/0x80
        kobject_del+0x18/0x50
        device_del+0x19f/0x260
        netdev_unregister_kobject+0x6a/0x80
        rollback_registered_many+0x1fd/0x340
        rollback_registered+0x3c/0x70
        unregister_netdevice_queue+0x55/0xc0
        unregister_netdev+0x20/0x30
        ipoib_remove_one+0x114/0x1b0 [ib_ipoib]
        ib_unregister_client+0x4a/0x170 [ib_core]
        ? find_module_all+0x71/0xa0
        ipoib_cleanup_module+0x10/0x94 [ib_ipoib]
        SyS_delete_module+0x1b5/0x210
        entry_SYSCALL_64_fastpath+0x16/0x75

The fix is by checking the flag IPOIB_FLAG_INTF_ON_DESTROY in order to
get out from the sysfs function.

Fixes: 862096a8 ("IB/ipoib: Add more rtnl_link_ops callbacks")
Fixes: 9baa0b03 ("IB/ipoib: Add rtnl_link_ops support")
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

parent d7012467

drivers/infiniband/ulp/ipoib/ipoib.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -94,6 +94,7 @@ enum {
		IPOIB_NEIGH_TBL_FLUSH = 12,
		IPOIB_FLAG_DEV_ADDR_SET = 13,
		IPOIB_FLAG_DEV_ADDR_CTRL = 14,
		IPOIB_FLAG_GOING_DOWN = 15,

		IPOIB_MAX_BACKOFF_SECONDS = 16,

drivers/infiniband/ulp/ipoib/ipoib_cm.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1486,6 +1486,10 @@ static ssize_t set_mode(struct device d, struct device_attribute attr,
		{
		struct net_device *dev = to_net_dev(d);
		int ret;
		struct ipoib_dev_priv *priv = netdev_priv(dev);

		if (test_bit(IPOIB_FLAG_GOING_DOWN, &priv->flags))
		return -EPERM;

		if (!rtnl_trylock())
		return restart_syscall();

drivers/infiniband/ulp/ipoib/ipoib_main.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2141,6 +2141,9 @@ static void ipoib_remove_one(struct ib_device device, void client_data)
		ib_unregister_event_handler(&priv->event_handler);
		flush_workqueue(ipoib_workqueue);

		/* mark interface in the middle of destruction */
		set_bit(IPOIB_FLAG_GOING_DOWN, &priv->flags);

		rtnl_lock();
		dev_change_flags(priv->dev, priv->dev->flags & ~IFF_UP);
		rtnl_unlock();

drivers/infiniband/ulp/ipoib/ipoib_vlan.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -131,6 +131,9 @@ int ipoib_vlan_add(struct net_device *pdev, unsigned short pkey)

		ppriv = netdev_priv(pdev);

		if (test_bit(IPOIB_FLAG_GOING_DOWN, &ppriv->flags))
		return -EPERM;

		snprintf(intf_name, sizeof intf_name, "%s.%04x",
		ppriv->dev->name, pkey);
		priv = ipoib_intf_alloc(intf_name);
		@@ -183,6 +186,9 @@ int ipoib_vlan_delete(struct net_device *pdev, unsigned short pkey)

		ppriv = netdev_priv(pdev);

		if (test_bit(IPOIB_FLAG_GOING_DOWN, &ppriv->flags))
		return -EPERM;

		if (!rtnl_trylock())
		return restart_syscall();