[Nouveau] [PATCH] nouveau/u_memcpya: fix NULL vs error pointer bug

[Danilo Krummrich]

On 9/16/23 16:24, Dan Carpenter wrote:
> On Sat, Sep 16, 2023 at 01:41:43AM +0200, Danilo Krummrich wrote:
>> Hi Dan,
>>
>> On 9/15/23 14:59, Dan Carpenter wrote:
>>> The u_memcpya() function is supposed to return error pointers on
>>> error.  Returning NULL will lead to an Oops.
>>>
>>> Fixes: 68132cc6d1bc ("nouveau/u_memcpya: use vmemdup_user")
>>> Signed-off-by: Dan Carpenter <dan.carpenter at linaro.org>
>>> ---
>>>    drivers/gpu/drm/nouveau/nouveau_drv.h | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h
>>> index 3666a7403e47..52a708a98915 100644
>>> --- a/drivers/gpu/drm/nouveau/nouveau_drv.h
>>> +++ b/drivers/gpu/drm/nouveau/nouveau_drv.h
>>> @@ -193,7 +193,7 @@ u_memcpya(uint64_t user, unsigned int nmemb, unsigned int size)
>>>    	size_t bytes;
>>>    	if (unlikely(check_mul_overflow(nmemb, size, &bytes)))
>>> -		return NULL;
>>> +		return ERR_PTR(-ENOMEM);
>>
>> I plan to replace this function with an upcoming vmemdup_array_user() helper,
>> which returns -EOVERFLOW instead, hence mind using that?
>>
>> Unless you disagree, no need to resubmit the patch, I can change it
>> before applying the patch.
> 
> Generally, I would say that ENOMEM is the correct error code.  I feel
> like someone thinks EOVERFLOW means integer overflow and that's not
> correct.  I means like if you pass a number higher than INT_MAX to
> kstroint().
> 
> But I don't care strongly about this.  You can change it if you want to.

I seems that vmemdup_array_user() will keep using EOVERFLOW, hence aligning to
that.

Pushed the patch to drm-misc-fixes, thanks!

> 
> regards,
> dan carpenter
>