[PATCH] iommu/iova: validate iova_domain input to put_iova_domain

[PATCH] iommu/iova: validate iova_domain input to put_iova_domain

[Nate Watterson]

Passing a NULL or uninitialized iova_domain into put_iova_domain
will currently crash the kernel when the unconfigured iova_domain
data members are accessed. To prevent this from occurring, this patch
adds a check to make sure that the domain is non-NULL and that the
domain granule is non-zero. The granule can be used to check if the
domain was properly initialized because calling init_iova_domain
with a granule of zero would have already triggered a BUG statement
crashing the kernel.

Signed-off-by: Nate Watterson <nwatters-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
---
 drivers/iommu/iova.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index e23001b..3511a1c 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -459,6 +459,10 @@ void put_iova_domain(struct iova_domain *iovad)
 	struct rb_node *node;
 	unsigned long flags;
 
+	/* Only teardown properly initialized domains */
+	if (!iovad || !iovad->granule)
+		return;
+
 	free_iova_rcaches(iovad);
 	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
 	node = rb_first(&iovad->rbroot);
-- 
Qualcomm Datacenter Technologies, Inc. on behalf of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux
Foundation Collaborative Project.

Re: [PATCH] iommu/iova: validate iova_domain input to put_iova_domain

[Joerg Roedel]

On Wed, Jul 13, 2016 at 02:49:32PM -0400, Nate Watterson wrote:
> Passing a NULL or uninitialized iova_domain into put_iova_domain
> will currently crash the kernel when the unconfigured iova_domain
> data members are accessed. To prevent this from occurring, this patch
> adds a check to make sure that the domain is non-NULL and that the
> domain granule is non-zero. The granule can be used to check if the
> domain was properly initialized because calling init_iova_domain
> with a granule of zero would have already triggered a BUG statement
> crashing the kernel.

Have you seen real crashes happening because of this?


	Joerg

Re: [PATCH] iommu/iova: validate iova_domain input to put_iova_domain

[Robin Murphy]

On 14/07/16 09:34, Joerg Roedel wrote:
> On Wed, Jul 13, 2016 at 02:49:32PM -0400, Nate Watterson wrote:
>> Passing a NULL or uninitialized iova_domain into put_iova_domain
>> will currently crash the kernel when the unconfigured iova_domain
>> data members are accessed. To prevent this from occurring, this patch
>> adds a check to make sure that the domain is non-NULL and that the
>> domain granule is non-zero. The granule can be used to check if the
>> domain was properly initialized because calling init_iova_domain
>> with a granule of zero would have already triggered a BUG statement
>> crashing the kernel.
> 
> Have you seen real crashes happening because of this?

It _can_ happen via the iommu-dma code if something goes wrong
initialising a group - the IOVA domain gets allocated at the same time
as the default IOMMU domain, but isn't initialised until later once the
device in question gets ity dma ops set up. If adding the device to the
group fails, everything gets torn down again and iommu_put_dma_cookie()
ends up trying to take an uninitialised lock .

However, I think the appropriate fix for that particular situation would
be more like this:

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index ea5a9ebf0f78..d00d22930a6b 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -65,10 +65,11 @@ void iommu_put_dma_cookie(struct iommu_domain *domain)
 {
        struct iova_domain *iovad = domain->iova_cookie;

-       if (!iovad)
+       if (domain->type != IOMMU_DOMAIN_DMA || !iovad)
                return;

-       put_iova_domain(iovad);
+       if (iovad->granule)
+               put_iova_domain(iovad);
        kfree(iovad);
        domain->iova_cookie = NULL;
 }

(It probably should have been that way from the start; mea culpa)

Robin.

Re: [PATCH] iommu/iova: validate iova_domain input to put_iova_domain

[Auger Eric]

Hi Robin, Nate,
On 14/07/2016 12:36, Robin Murphy wrote:
> On 14/07/16 09:34, Joerg Roedel wrote:
>> On Wed, Jul 13, 2016 at 02:49:32PM -0400, Nate Watterson wrote:
>>> Passing a NULL or uninitialized iova_domain into put_iova_domain
>>> will currently crash the kernel when the unconfigured iova_domain
>>> data members are accessed. To prevent this from occurring, this patch
>>> adds a check to make sure that the domain is non-NULL and that the
>>> domain granule is non-zero. The granule can be used to check if the
>>> domain was properly initialized because calling init_iova_domain
>>> with a granule of zero would have already triggered a BUG statement
>>> crashing the kernel.
>>
>> Have you seen real crashes happening because of this?

I also saw the crash happening with my PCIe passthrough series (not
upstreamed)
[PATCH v10 0/8] [PATCH v10 0/8] KVM PCIe/MSI passthrough on ARM/ARM64:
kernel part 1/3: iommu changes  https://lkml.org/lkml/2016/6/7/676

patch [PATCH v10 8/8] iommu/arm-smmu: get/put the msi cookie
also uses iommu_put_dma_cookie


and the uninitialised lock crash happens if the group gets destroyed
before the iommu_dma_init_domain is called, which can also happen for me.

> 
> It _can_ happen via the iommu-dma code if something goes wrong
> initialising a group - the IOVA domain gets allocated at the same time
> as the default IOMMU domain, but isn't initialised until later once the
> device in question gets ity dma ops set up. If adding the device to the
> group fails, everything gets torn down again and iommu_put_dma_cookie()
> ends up trying to take an uninitialised lock .
Cant' we allow the granule check also with UNMANAGED type?

Thanks

Eric

> 
> However, I think the appropriate fix for that particular situation would
> be more like this:
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index ea5a9ebf0f78..d00d22930a6b 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -65,10 +65,11 @@ void iommu_put_dma_cookie(struct iommu_domain *domain)
>  {
>         struct iova_domain *iovad = domain->iova_cookie;
> 
> -       if (!iovad)
> +       if (domain->type != IOMMU_DOMAIN_DMA || !iovad)
>                 return;
> 
> -       put_iova_domain(iovad);
> +       if (iovad->granule)
> +               put_iova_domain(iovad);
>         kfree(iovad);
>         domain->iova_cookie = NULL;
>  }
> 
> (It probably should have been that way from the start; mea culpa)
> 
> Robin.
> _______________________________________________
> iommu mailing list
> iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> 

Re: [PATCH] iommu/iova: validate iova_domain input to put_iova_domain

[nwatters-sgV2jX0FEOL9JmXXK+q4OQ]

On 2016-07-14 07:21, Auger Eric wrote:
> Hi Robin, Nate,
> On 14/07/2016 12:36, Robin Murphy wrote:
>> On 14/07/16 09:34, Joerg Roedel wrote:
>>> On Wed, Jul 13, 2016 at 02:49:32PM -0400, Nate Watterson wrote:
>>>> Passing a NULL or uninitialized iova_domain into put_iova_domain
>>>> will currently crash the kernel when the unconfigured iova_domain
>>>> data members are accessed. To prevent this from occurring, this 
>>>> patch
>>>> adds a check to make sure that the domain is non-NULL and that the
>>>> domain granule is non-zero. The granule can be used to check if the
>>>> domain was properly initialized because calling init_iova_domain
>>>> with a granule of zero would have already triggered a BUG statement
>>>> crashing the kernel.
>>> 
>>> Have you seen real crashes happening because of this?

In my case, it was calling iommu_request_dm_for_dev() which triggered 
the
"iommu_[get/put]_dma_cookie() without iommu_dma_init_domain()" issue 
that
has Robin documented below.

> 
> I also saw the crash happening with my PCIe passthrough series (not
> upstreamed)
> [PATCH v10 0/8] [PATCH v10 0/8] KVM PCIe/MSI passthrough on ARM/ARM64:
> kernel part 1/3: iommu changes  https://lkml.org/lkml/2016/6/7/676
> 
> patch [PATCH v10 8/8] iommu/arm-smmu: get/put the msi cookie
> also uses iommu_put_dma_cookie
> 
> 
> and the uninitialised lock crash happens if the group gets destroyed
> before the iommu_dma_init_domain is called, which can also happen for 
> me.
> 
>> 
>> It _can_ happen via the iommu-dma code if something goes wrong
>> initialising a group - the IOVA domain gets allocated at the same time
>> as the default IOMMU domain, but isn't initialised until later once 
>> the
>> device in question gets ity dma ops set up. If adding the device to 
>> the
>> group fails, everything gets torn down again and 
>> iommu_put_dma_cookie()
>> ends up trying to take an uninitialised lock .
> Cant' we allow the granule check also with UNMANAGED type?
> 
> Thanks
> 
> Eric
> 
>> 
>> However, I think the appropriate fix for that particular situation 
>> would
>> be more like this:
>> 
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index ea5a9ebf0f78..d00d22930a6b 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -65,10 +65,11 @@ void iommu_put_dma_cookie(struct iommu_domain 
>> *domain)
>>  {
>>         struct iova_domain *iovad = domain->iova_cookie;
>> 
>> -       if (!iovad)
>> +       if (domain->type != IOMMU_DOMAIN_DMA || !iovad)
>>                 return;
>> 
>> -       put_iova_domain(iovad);
>> +       if (iovad->granule)
>> +               put_iova_domain(iovad);
>>         kfree(iovad);
>>         domain->iova_cookie = NULL;
>>  }
>> 
>> (It probably should have been that way from the start; mea culpa)

I originally put together a similar patch, but then thought that people 
would
complain it didn't fix the root of the problem. Yet another instance 
where
thinking was best avoided I guess.

>> 
>> Robin.
>> _______________________________________________
>> iommu mailing list
>> iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>> 

-- 
Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm 
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a 
Linux Foundation Collaborative Project.