Nouveau - Sep 2023 - [PATCH] nouveau/u_memcpya: fix NULL vs error pointer bug

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.

- Danilo
>   	return vmemdup_user(userptr, bytes);
>   }
>

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.

regards,
dan carpenter