[PATCH][next] iommu/vt-d: Fix out-bounds-warning in intel_svm_page_response()

[PATCH][next] iommu/vt-d: Fix out-bounds-warning in intel_svm_page_response()

[Gustavo A. R. Silva]

Replace call to memcpy() with just a couple of simple assignments in
order to fix the following out-of-bounds warning:

drivers/iommu/intel/svm.c:1198:4: warning: 'memcpy' offset [25, 32] from the object at 'desc' is out of the bounds of referenced subobject 'qw2' with type 'long long unsigned int' at offset 16 [-Warray-bounds]

The problem is that the original code is trying to copy data into a
couple of struct members adjacent to each other in a single call to
memcpy(). This causes a legitimate compiler warning because memcpy()
overruns the length of &desc.qw2.

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/iommu/intel/svm.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 5165cea90421..65909f504c50 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -1194,9 +1194,10 @@ int intel_svm_page_response(struct device *dev,
 		desc.qw1 = QI_PGRP_IDX(prm->grpid) | QI_PGRP_LPIG(last_page);
 		desc.qw2 = 0;
 		desc.qw3 = 0;
-		if (private_present)
-			memcpy(&desc.qw2, prm->private_data,
-			       sizeof(prm->private_data));
+		if (private_present) {
+			desc.qw2 = prm->private_data[0];
+			desc.qw3 = prm->private_data[1];
+		}
 
 		qi_submit_sync(iommu, &desc, 1, 0);
 	}
-- 
2.27.0

Re: [PATCH][next] iommu/vt-d: Fix out-bounds-warning in intel_svm_page_response()

[Lu Baolu]

Hi Gustavo,

On 4/14/21 3:54 AM, Gustavo A. R. Silva wrote:
> Replace call to memcpy() with just a couple of simple assignments in
> order to fix the following out-of-bounds warning:
> 
> drivers/iommu/intel/svm.c:1198:4: warning: 'memcpy' offset [25, 32] from the object at 'desc' is out of the bounds of referenced subobject 'qw2' with type 'long long unsigned int' at offset 16 [-Warray-bounds]
> 
> The problem is that the original code is trying to copy data into a
> couple of struct members adjacent to each other in a single call to
> memcpy(). This causes a legitimate compiler warning because memcpy()
> overruns the length of &desc.qw2.
> 
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
> 
> Link: https://github.com/KSPP/linux/issues/109
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>   drivers/iommu/intel/svm.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index 5165cea90421..65909f504c50 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -1194,9 +1194,10 @@ int intel_svm_page_response(struct device *dev,
>   		desc.qw1 = QI_PGRP_IDX(prm->grpid) | QI_PGRP_LPIG(last_page);
>   		desc.qw2 = 0;
>   		desc.qw3 = 0;
> -		if (private_present)
> -			memcpy(&desc.qw2, prm->private_data,
> -			       sizeof(prm->private_data));

The same memcpy() is used in multiple places in this file. Did they
compile the same warnings? Or there are multiple patches to fix them
one by one?

Best regards,
baolu

> +		if (private_present) {
> +			desc.qw2 = prm->private_data[0];
> +			desc.qw3 = prm->private_data[1];
> +		}
>   
>   		qi_submit_sync(iommu, &desc, 1, 0);
>   	}
> 

Re: [PATCH][next] iommu/vt-d: Fix out-bounds-warning in intel_svm_page_response()

[Gustavo A. R. Silva]

Hi Balou,

On 4/14/21 00:24, Lu Baolu wrote:
> Hi Gustavo,
> 
> On 4/14/21 3:54 AM, Gustavo A. R. Silva wrote:
>> Replace call to memcpy() with just a couple of simple assignments in
>> order to fix the following out-of-bounds warning:
>>
>> drivers/iommu/intel/svm.c:1198:4: warning: 'memcpy' offset [25, 32] from the object at 'desc' is out of the bounds of referenced subobject 'qw2' with type
>> 'long long unsigned int' at offset 16 [-Warray-bounds]
>>
>> The problem is that the original code is trying to copy data into a
>> couple of struct members adjacent to each other in a single call to
>> memcpy(). This causes a legitimate compiler warning because memcpy()
>> overruns the length of &desc.qw2.
>>
>> This helps with the ongoing efforts to globally enable -Warray-bounds
>> and get us closer to being able to tighten the FORTIFY_SOURCE routines
>> on memcpy().
>>
>> Link: https://github.com/KSPP/linux/issues/109
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>>   drivers/iommu/intel/svm.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
>> index 5165cea90421..65909f504c50 100644
>> --- a/drivers/iommu/intel/svm.c
>> +++ b/drivers/iommu/intel/svm.c
>> @@ -1194,9 +1194,10 @@ int intel_svm_page_response(struct device *dev,
>>           desc.qw1 = QI_PGRP_IDX(prm->grpid) | QI_PGRP_LPIG(last_page);
>>           desc.qw2 = 0;
>>           desc.qw3 = 0;
>> -        if (private_present)
>> -            memcpy(&desc.qw2, prm->private_data,
>> -                   sizeof(prm->private_data));
> 
> The same memcpy() is used in multiple places in this file. Did they
> compile the same warnings? Or there are multiple patches to fix them
> one by one?

I just see one more instance of this same case:

1023                         if (req->priv_data_present)
1024                                 memcpy(&resp.qw2, req->priv_data,
1025                                        sizeof(req->priv_data));

I missed it and I'll address it in v2. Do you see another one?

Thanks for the feedback!
--
Gustavo