linux-kernel - Re: [PATCH] iommu: WARN_ON when removing a device with no iommu

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Date:	Tue, 3 Sep 2013 11:15:44 +0800
From:	Wei Yang <weiyang@...ux.vnet.ibm.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	Wei Yang <weiyang@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	aik@...abs.ru, paulus@....ibm.com, benh@....ibm.com,
	iommu <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH] iommu: WARN_ON when removing a device with no
 iommu_group associated

Any more comments? Or this one is not proper?

On Thu, Aug 22, 2013 at 09:33:27PM -0600, Alex Williamson wrote:
>[+cc iommu]
>
>On Fri, 2013-08-23 at 09:55 +0800, Wei Yang wrote:
>> When removing a device from the system, iommu_group driver will try to
>> disconnect it from its group. While in some cases, one device may not
>> associated with any iommu_group. For example, not enough DMA address space.
>> 
>> In the generic bus notification, it will check dev->iommu_group before calling
>> iommu_group_remove_device(). While in some cases, developers may call
>> iommu_group_remove_device() in a different code path and without check. For
>> those devices with dev->iommu_group set to NULL, kernel will crash.
>> 
>> This patch gives a warning and return when trying to remove a device from an
>> iommu_group with dev->iommu_group set to NULL. This helps to indicate some bad
>> behavior and also guard the kernel.
>> 
>> Signed-off-by: Wei Yang <weiyang@...ux.vnet.ibm.com>
>
>Acked-by: Alex Williamson <alex.williamson@...hat.com>
>
>> ---
>>  drivers/iommu/iommu.c |    3 +++
>>  1 files changed, 3 insertions(+), 0 deletions(-)
>> 
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index fbe9ca7..43396f0 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -379,6 +379,9 @@ void iommu_group_remove_device(struct device *dev)
>>  	struct iommu_group *group = dev->iommu_group;
>>  	struct iommu_device *tmp_device, *device = NULL;
>>  
>> +	if (WARN_ON(!group))
>> +		return;
>> +
>>  	/* Pre-notify listeners that a device is being removed. */
>>  	blocking_notifier_call_chain(&group->notifier,
>>  				     IOMMU_GROUP_NOTIFY_DEL_DEVICE, dev);
>
>

-- 
Richard Yang
Help you, Help me

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