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

[Dan Carpenter]

On Sat, Sep 16, 2023 at 05:24:04PM +0300, 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().

The most common error code for integer overflows is EINVAL because the
user passed invalid data.

regards,
dan carpenter