Re: [PATCHv2 3/7] crypto: omap-crypto: fix userspace copied buffer access

[Tero Kristo <t-kristo@ti.com>]

On 22/05/2020 16:12, Herbert Xu wrote:
> On Mon, May 11, 2020 at 02:19:09PM +0300, Tero Kristo wrote:
>> In case buffers are copied from userspace, directly accessing the page
>> will most likely fail because it hasn't been mapped into the kernel
>> memory space. Fix the issue by forcing a kmap / kunmap within the
>> cleanup functionality.
>>
>> Signed-off-by: Tero Kristo <t-kristo@ti.com>
>> ---
>>   drivers/crypto/omap-crypto.c | 9 +++++++--
>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/crypto/omap-crypto.c b/drivers/crypto/omap-crypto.c
>> index cc88b7362bc2..31bdb1d76d11 100644
>> --- a/drivers/crypto/omap-crypto.c
>> +++ b/drivers/crypto/omap-crypto.c
>> @@ -178,11 +178,16 @@ static void omap_crypto_copy_data(struct scatterlist *src,
>>   		amt = min(src->length - srco, dst->length - dsto);
>>   		amt = min(len, amt);
>>   
>> -		srcb = sg_virt(src) + srco;
>> -		dstb = sg_virt(dst) + dsto;
>> +		srcb = kmap_atomic(sg_page(src)) + srco + src->offset;
>> +		dstb = kmap_atomic(sg_page(dst)) + dsto + dst->offset;
>>   
>>   		memcpy(dstb, srcb, amt);
>>   
>> +		flush_dcache_page(sg_page(dst));
> 
> You need to check !PageSlab as it's illegal to call it on a kernel
> page.  Also you should be using flush_kernel_dcache_page.  scatterwalk
> uses flush_dcache_page only because when it was created the other
> function didn't exist.

Ok will fix that.

> Would it be possible to use the sg_miter interface to do the copy?
> In fact your function could possibly be added to lib/scatterlist.c
> as it seems to be quite generic.

I think it would make sense to use that, however as I am just fixing an 
existing bug here, would it be ok if I just fix your above comment and 
post v3? I can convert this later to sg_miter and take a shot at moving 
this to lib/scatterlist.c as that seems slightly bigger effort and I 
would not want to block this whole series because of that...

-Tero
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