powerpc/book3s64: Fix error handling in mm_iommu_do_alloc()

The last jump to free_exit in mm_iommu_do_alloc() happens after page
pointers in struct mm_iommu_table_group_mem_t were already converted to
physical addresses. Thus calling put_page() on these physical addresses
will likely crash. Convert physical addresses back to page pointers
during the error cleanup.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 arch/powerpc/mm/book3s64/iommu_api.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

 Beware, this is completely untested, spotted just by code audit.

On 11/12/2019 21:42, Jan Kara wrote:
> The last jump to free_exit in mm_iommu_do_alloc() happens after page
> pointers in struct mm_iommu_table_group_mem_t were already converted to
> physical addresses. Thus calling put_page() on these physical addresses
> will likely crash. Convert physical addresses back to page pointers
> during the error cleanup.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  arch/powerpc/mm/book3s64/iommu_api.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
>  Beware, this is completely untested, spotted just by code audit.
> 
> diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
> index 56cc84520577..06c403381c9c 100644
> --- a/arch/powerpc/mm/book3s64/iommu_api.c
> +++ b/arch/powerpc/mm/book3s64/iommu_api.c
> @@ -154,7 +154,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
>  				       (mem2->entries << PAGE_SHIFT)))) {
>  			ret = -EINVAL;
>  			mutex_unlock(&mem_list_mutex);
> -			goto free_exit;
> +			goto convert_exit;
>  		}
>  	}
>  
> @@ -166,6 +166,9 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
>  
>  	return 0;
>  
> +convert_exit:
> +	for (i = 0; i < pinned; i++)
> +		mem->hpages[i] = pfn_to_page(mem->hpas[i] >> PAGE_SHIFT);


Good find. Although doing it where you added "goto convert_exit" seems
cleaner imho. Thanks,


>  free_exit:
>  	/* free the reference taken */
>  	for (i = 0; i < pinned; i++)
>

On Fri 20-12-19 16:06:05, Alexey Kardashevskiy wrote:
> 
> 
> On 11/12/2019 21:42, Jan Kara wrote:
> > The last jump to free_exit in mm_iommu_do_alloc() happens after page
> > pointers in struct mm_iommu_table_group_mem_t were already converted to
> > physical addresses. Thus calling put_page() on these physical addresses
> > will likely crash. Convert physical addresses back to page pointers
> > during the error cleanup.
> > 
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> >  arch/powerpc/mm/book3s64/iommu_api.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> >  Beware, this is completely untested, spotted just by code audit.
> > 
> > diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
> > index 56cc84520577..06c403381c9c 100644
> > --- a/arch/powerpc/mm/book3s64/iommu_api.c
> > +++ b/arch/powerpc/mm/book3s64/iommu_api.c
> > @@ -154,7 +154,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
> >  				       (mem2->entries << PAGE_SHIFT)))) {
> >  			ret = -EINVAL;
> >  			mutex_unlock(&mem_list_mutex);
> > -			goto free_exit;
> > +			goto convert_exit;
> >  		}
> >  	}
> >  
> > @@ -166,6 +166,9 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
> >  
> >  	return 0;
> >  
> > +convert_exit:
> > +	for (i = 0; i < pinned; i++)
> > +		mem->hpages[i] = pfn_to_page(mem->hpas[i] >> PAGE_SHIFT);
> 
> 
> Good find. Although doing it where you added "goto convert_exit" seems
> cleaner imho. Thanks,

I don't really care :). V2 attached.

								Honza

On 20/12/2019 20:57, Jan Kara wrote:
> On Fri 20-12-19 16:06:05, Alexey Kardashevskiy wrote:
>>
>>
>> On 11/12/2019 21:42, Jan Kara wrote:
>>> The last jump to free_exit in mm_iommu_do_alloc() happens after page
>>> pointers in struct mm_iommu_table_group_mem_t were already converted to
>>> physical addresses. Thus calling put_page() on these physical addresses
>>> will likely crash. Convert physical addresses back to page pointers
>>> during the error cleanup.
>>>
>>> Signed-off-by: Jan Kara <jack@suse.cz>
>>> ---
>>>  arch/powerpc/mm/book3s64/iommu_api.c | 5 ++++-
>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>>  Beware, this is completely untested, spotted just by code audit.
>>>
>>> diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
>>> index 56cc84520577..06c403381c9c 100644
>>> --- a/arch/powerpc/mm/book3s64/iommu_api.c
>>> +++ b/arch/powerpc/mm/book3s64/iommu_api.c
>>> @@ -154,7 +154,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
>>>  				       (mem2->entries << PAGE_SHIFT)))) {
>>>  			ret = -EINVAL;
>>>  			mutex_unlock(&mem_list_mutex);
>>> -			goto free_exit;
>>> +			goto convert_exit;
>>>  		}
>>>  	}
>>>  
>>> @@ -166,6 +166,9 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
>>>  
>>>  	return 0;
>>>  
>>> +convert_exit:
>>> +	for (i = 0; i < pinned; i++)
>>> +		mem->hpages[i] = pfn_to_page(mem->hpas[i] >> PAGE_SHIFT);
>>
>>
>> Good find. Although doing it where you added "goto convert_exit" seems
>> cleaner imho. Thanks,
> 
> I don't really care :). V2 attached.


Usually patches are posted using git send-mail, not as attachment. A
nit: v2 has now curly braces which v1 did not.

Either way, v2 is correct.


Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>