[PATCH] drm/nouveau/nvif: Avoid build error due to potential integer overflows

[PATCH] drm/nouveau/nvif: Avoid build error due to potential integer overflows

[Guenter Roeck]

Trying to build parisc:allmodconfig with gcc 12.x or later results
in the following build error.

drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_mthd':
drivers/gpu/drm/nouveau/nvif/object.c:161:9: error:
	'memcpy' accessing 4294967264 or more bytes at offsets 0 and 32 overlaps 6442450881 bytes at offset -2147483617 [-Werror=restrict]
  161 |         memcpy(data, args->mthd.data, size);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_ctor':
drivers/gpu/drm/nouveau/nvif/object.c:298:17: error:
	'memcpy' accessing 4294967240 or more bytes at offsets 0 and 56 overlaps 6442450833 bytes at offset -2147483593 [-Werror=restrict]
  298 |                 memcpy(data, args->new.data, size);

gcc assumes that 'sizeof(*args) + size' can overflow, which would result
in the problem.

The problem is not new, only it is now no longer a warning but an error since W=1
has been enabled for the drm subsystem and since Werror is enabled for test builds.

Rearrange arithmetic and add extra size checks to avoid the overflow.

Fixes: a61ddb4393ad ("drm: enable (most) W=1 warnings by default across the subsystem")
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Danilo Krummrich <dakr@redhat.com>
Cc: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
checkpatch complains about the line length in the description and the (pre-existing)
assignlemts in if conditions, but I did not want to split lines in the description
or rearrange the code further.

I don't know why I only see the problem with parisc builds (at least so far).

 drivers/gpu/drm/nouveau/nvif/object.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
index 4d1aaee8fe15..baf623a48874 100644
--- a/drivers/gpu/drm/nouveau/nvif/object.c
+++ b/drivers/gpu/drm/nouveau/nvif/object.c
@@ -145,8 +145,9 @@ nvif_object_mthd(struct nvif_object *object, u32 mthd, void *data, u32 size)
 	u8 stack[128];
 	int ret;
 
-	if (sizeof(*args) + size > sizeof(stack)) {
-		if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
+	if (size > sizeof(stack) - sizeof(*args)) {
+		if (size > INT_MAX ||
+		    !(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
 			return -ENOMEM;
 	} else {
 		args = (void *)stack;
@@ -276,7 +277,8 @@ nvif_object_ctor(struct nvif_object *parent, const char *name, u32 handle,
 	object->map.size = 0;
 
 	if (parent) {
-		if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL))) {
+		if (size > INT_MAX ||
+		    !(args = kmalloc(sizeof(*args) + size, GFP_KERNEL))) {
 			nvif_object_dtor(object);
 			return -ENOMEM;
 		}
-- 
2.39.2

Re: [PATCH] drm/nouveau/nvif: Avoid build error due to potential integer overflows

[Christophe JAILLET]

(adding linux-hardening@vger.kernel.org)


Le 18/05/2024 à 16:37, Guenter Roeck a écrit :
> Trying to build parisc:allmodconfig with gcc 12.x or later results
> in the following build error.
> 
> drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_mthd':
> drivers/gpu/drm/nouveau/nvif/object.c:161:9: error:
> 	'memcpy' accessing 4294967264 or more bytes at offsets 0 and 32 overlaps 6442450881 bytes at offset -2147483617 [-Werror=restrict]
>    161 |         memcpy(data, args->mthd.data, size);
>        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_ctor':
> drivers/gpu/drm/nouveau/nvif/object.c:298:17: error:
> 	'memcpy' accessing 4294967240 or more bytes at offsets 0 and 56 overlaps 6442450833 bytes at offset -2147483593 [-Werror=restrict]
>    298 |                 memcpy(data, args->new.data, size);
> 
> gcc assumes that 'sizeof(*args) + size' can overflow, which would result
> in the problem.
> 
> The problem is not new, only it is now no longer a warning but an error since W=1
> has been enabled for the drm subsystem and since Werror is enabled for test builds.
> 
> Rearrange arithmetic and add extra size checks to avoid the overflow.
> 
> Fixes: a61ddb4393ad ("drm: enable (most) W=1 warnings by default across the subsystem")
> Cc: Javier Martinez Canillas <javierm-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Jani Nikula <jani.nikula-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Cc: Thomas Zimmermann <tzimmermann-l3A5Bk7waGM@public.gmane.org>
> Cc: Danilo Krummrich <dakr-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Maxime Ripard <mripard-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Signed-off-by: Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
> ---
> checkpatch complains about the line length in the description and the (pre-existing)
> assignlemts in if conditions, but I did not want to split lines in the description
> or rearrange the code further.
> 
> I don't know why I only see the problem with parisc builds (at least so far).
> 
>   drivers/gpu/drm/nouveau/nvif/object.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
> index 4d1aaee8fe15..baf623a48874 100644
> --- a/drivers/gpu/drm/nouveau/nvif/object.c
> +++ b/drivers/gpu/drm/nouveau/nvif/object.c
> @@ -145,8 +145,9 @@ nvif_object_mthd(struct nvif_object *object, u32 mthd, void *data, u32 size)
>   	u8 stack[128];
>   	int ret;
>   
> -	if (sizeof(*args) + size > sizeof(stack)) {
> -		if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
> +	if (size > sizeof(stack) - sizeof(*args)) {
> +		if (size > INT_MAX ||
> +		    !(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))

Hi,

Would it be cleaner or better to use size_add(sizeof(*args), size)?

>   			return -ENOMEM;
>   	} else {
>   		args = (void *)stack;
> @@ -276,7 +277,8 @@ nvif_object_ctor(struct nvif_object *parent, const char *name, u32 handle,
>   	object->map.size = 0;
>   
>   	if (parent) {
> -		if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL))) {
> +		if (size > INT_MAX ||
> +		    !(args = kmalloc(sizeof(*args) + size, GFP_KERNEL))) {

Same.

CJ

>   			nvif_object_dtor(object);
>   			return -ENOMEM;
>   		}

Re: [PATCH] drm/nouveau/nvif: Avoid build error due to potential integer overflows

[Kees Cook]

On Sat, May 18, 2024 at 06:54:36PM +0200, Christophe JAILLET wrote:
> (adding linux-hardening@vger.kernel.org)
> 
> 
> Le 18/05/2024 à 16:37, Guenter Roeck a écrit :
> > Trying to build parisc:allmodconfig with gcc 12.x or later results
> > in the following build error.
> > 
> > drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_mthd':
> > drivers/gpu/drm/nouveau/nvif/object.c:161:9: error:
> > 	'memcpy' accessing 4294967264 or more bytes at offsets 0 and 32 overlaps 6442450881 bytes at offset -2147483617 [-Werror=restrict]
> >    161 |         memcpy(data, args->mthd.data, size);
> >        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_ctor':
> > drivers/gpu/drm/nouveau/nvif/object.c:298:17: error:
> > 	'memcpy' accessing 4294967240 or more bytes at offsets 0 and 56 overlaps 6442450833 bytes at offset -2147483593 [-Werror=restrict]
> >    298 |                 memcpy(data, args->new.data, size);
> > 
> > gcc assumes that 'sizeof(*args) + size' can overflow, which would result
> > in the problem.
> > 
> > The problem is not new, only it is now no longer a warning but an error since W=1
> > has been enabled for the drm subsystem and since Werror is enabled for test builds.
> > 
> > Rearrange arithmetic and add extra size checks to avoid the overflow.
> > 
> > Fixes: a61ddb4393ad ("drm: enable (most) W=1 warnings by default across the subsystem")
> > Cc: Javier Martinez Canillas <javierm-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > Cc: Jani Nikula <jani.nikula-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > Cc: Thomas Zimmermann <tzimmermann-l3A5Bk7waGM@public.gmane.org>
> > Cc: Danilo Krummrich <dakr-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > Cc: Maxime Ripard <mripard-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> > Signed-off-by: Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
> > ---
> > checkpatch complains about the line length in the description and the (pre-existing)
> > assignlemts in if conditions, but I did not want to split lines in the description
> > or rearrange the code further.
> > 
> > I don't know why I only see the problem with parisc builds (at least so far).
> > 
> >   drivers/gpu/drm/nouveau/nvif/object.c | 8 +++++---
> >   1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
> > index 4d1aaee8fe15..baf623a48874 100644
> > --- a/drivers/gpu/drm/nouveau/nvif/object.c
> > +++ b/drivers/gpu/drm/nouveau/nvif/object.c
> > @@ -145,8 +145,9 @@ nvif_object_mthd(struct nvif_object *object, u32 mthd, void *data, u32 size)
> >   	u8 stack[128];
> >   	int ret;
> > -	if (sizeof(*args) + size > sizeof(stack)) {
> > -		if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
> > +	if (size > sizeof(stack) - sizeof(*args)) {
> > +		if (size > INT_MAX ||
> > +		    !(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
> 
> Hi,
> 
> Would it be cleaner or better to use size_add(sizeof(*args), size)?

I think the INT_MAX test is actually better in this case because
nvif_object_ioctl()'s size argument is u32:

ret = nvif_object_ioctl(object, args, sizeof(*args) + size, NULL);
                                      ^^^^^^^^^^^^^^^^^^^^

So that could wrap around, even though the allocation may not.

Better yet, since "sizeof(*args) + size" is repeated 3 times in the
function, I'd recommend:

	...
	u32 args_size;

	if (check_add_overflow(sizeof(*args), size, &args_size))
		return -ENOMEM;
	if (args_size > sizeof(stack)) {
		if (!(args = kmalloc(args_size, GFP_KERNEL)))
			return -ENOMEM;
        } else {
                args = (void *)stack;
        }
	...
        ret = nvif_object_ioctl(object, args, args_size, NULL);

This will catch the u32 overflow to nvif_object_ioctl(), catch an
allocation underflow on 32-bits systems, and make the code more
readable. :)

-Kees

-- 
Kees Cook

Re: [PATCH] drm/nouveau/nvif: Avoid build error due to potential integer overflows

[Guenter Roeck]

On 5/18/24 10:32, Kees Cook wrote:
> On Sat, May 18, 2024 at 06:54:36PM +0200, Christophe JAILLET wrote:
>> (adding linux-hardening@vger.kernel.org)
>>
>>
>> Le 18/05/2024 à 16:37, Guenter Roeck a écrit :
>>> Trying to build parisc:allmodconfig with gcc 12.x or later results
>>> in the following build error.
>>>
>>> drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_mthd':
>>> drivers/gpu/drm/nouveau/nvif/object.c:161:9: error:
>>> 	'memcpy' accessing 4294967264 or more bytes at offsets 0 and 32 overlaps 6442450881 bytes at offset -2147483617 [-Werror=restrict]
>>>     161 |         memcpy(data, args->mthd.data, size);
>>>         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_ctor':
>>> drivers/gpu/drm/nouveau/nvif/object.c:298:17: error:
>>> 	'memcpy' accessing 4294967240 or more bytes at offsets 0 and 56 overlaps 6442450833 bytes at offset -2147483593 [-Werror=restrict]
>>>     298 |                 memcpy(data, args->new.data, size);
>>>
>>> gcc assumes that 'sizeof(*args) + size' can overflow, which would result
>>> in the problem.
>>>
>>> The problem is not new, only it is now no longer a warning but an error since W=1
>>> has been enabled for the drm subsystem and since Werror is enabled for test builds.
>>>
>>> Rearrange arithmetic and add extra size checks to avoid the overflow.
>>>
>>> Fixes: a61ddb4393ad ("drm: enable (most) W=1 warnings by default across the subsystem")
>>> Cc: Javier Martinez Canillas <javierm-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>> Cc: Jani Nikula <jani.nikula-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>>> Cc: Thomas Zimmermann <tzimmermann-l3A5Bk7waGM@public.gmane.org>
>>> Cc: Danilo Krummrich <dakr-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>> Cc: Maxime Ripard <mripard-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
>>> Signed-off-by: Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
>>> ---
>>> checkpatch complains about the line length in the description and the (pre-existing)
>>> assignlemts in if conditions, but I did not want to split lines in the description
>>> or rearrange the code further.
>>>
>>> I don't know why I only see the problem with parisc builds (at least so far).
>>>
>>>    drivers/gpu/drm/nouveau/nvif/object.c | 8 +++++---
>>>    1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
>>> index 4d1aaee8fe15..baf623a48874 100644
>>> --- a/drivers/gpu/drm/nouveau/nvif/object.c
>>> +++ b/drivers/gpu/drm/nouveau/nvif/object.c
>>> @@ -145,8 +145,9 @@ nvif_object_mthd(struct nvif_object *object, u32 mthd, void *data, u32 size)
>>>    	u8 stack[128];
>>>    	int ret;
>>> -	if (sizeof(*args) + size > sizeof(stack)) {
>>> -		if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
>>> +	if (size > sizeof(stack) - sizeof(*args)) {
>>> +		if (size > INT_MAX ||
>>> +		    !(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
>>
>> Hi,
>>
>> Would it be cleaner or better to use size_add(sizeof(*args), size)?
> 
> I think the INT_MAX test is actually better in this case because
> nvif_object_ioctl()'s size argument is u32:
> 
> ret = nvif_object_ioctl(object, args, sizeof(*args) + size, NULL);
>                                        ^^^^^^^^^^^^^^^^^^^^
> 
> So that could wrap around, even though the allocation may not.
> 
> Better yet, since "sizeof(*args) + size" is repeated 3 times in the
> function, I'd recommend:
> 
> 	...
> 	u32 args_size;
> 
> 	if (check_add_overflow(sizeof(*args), size, &args_size))
> 		return -ENOMEM;
> 	if (args_size > sizeof(stack)) {
> 		if (!(args = kmalloc(args_size, GFP_KERNEL)))
> 			return -ENOMEM;
>          } else {
>                  args = (void *)stack;
>          }
> 	...
>          ret = nvif_object_ioctl(object, args, args_size, NULL);
> 
> This will catch the u32 overflow to nvif_object_ioctl(), catch an
> allocation underflow on 32-bits systems, and make the code more
> readable. :)
> 

Makes sense. I'll change that and send v2.

Thanks,
Guenter

Re: [PATCH] drm/nouveau/nvif: Avoid build error due to potential integer overflows

[Joe Perches]

On Sat, 2024-05-18 at 11:23 -0700, Guenter Roeck wrote:
> On 5/18/24 10:32, Kees Cook wrote:
> 
[]
> > I think the INT_MAX test is actually better in this case because
> > nvif_object_ioctl()'s size argument is u32:
> > 
> > ret = nvif_object_ioctl(object, args, sizeof(*args) + size, NULL);
> >                                        ^^^^^^^^^^^^^^^^^^^^
> > 
> > So that could wrap around, even though the allocation may not.
> > 
> > Better yet, since "sizeof(*args) + size" is repeated 3 times in the
> > function, I'd recommend:
> > 
> > 	...
> > 	u32 args_size;
> > 
> > 	if (check_add_overflow(sizeof(*args), size, &args_size))
> > 		return -ENOMEM;
> > 	if (args_size > sizeof(stack)) {
> > 		if (!(args = kmalloc(args_size, GFP_KERNEL)))

trivia:

More typical kernel style would use separate alloc and test

		args = kmalloc(args_size, GFP_KERNEL);
		if (!args)

> > 			return -ENOMEM;
> >          } else {
> >                  args = (void *)stack;
> >          }
> > 	...
> >          ret = nvif_object_ioctl(object, args, args_size, NULL);
> > 
> > This will catch the u32 overflow to nvif_object_ioctl(), catch an
> > allocation underflow on 32-bits systems, and make the code more
> > readable. :)
> > 
> 
> Makes sense. I'll change that and send v2.
> 
> Thanks,
> Guenter
> 
> 

Re: [PATCH] drm/nouveau/nvif: Avoid build error due to potential integer overflows

[Guenter Roeck]

On 5/18/24 18:19, Joe Perches wrote:
> On Sat, 2024-05-18 at 11:23 -0700, Guenter Roeck wrote:
>> On 5/18/24 10:32, Kees Cook wrote:
>>
> []
>>> I think the INT_MAX test is actually better in this case because
>>> nvif_object_ioctl()'s size argument is u32:
>>>
>>> ret = nvif_object_ioctl(object, args, sizeof(*args) + size, NULL);
>>>                                         ^^^^^^^^^^^^^^^^^^^^
>>>
>>> So that could wrap around, even though the allocation may not.
>>>
>>> Better yet, since "sizeof(*args) + size" is repeated 3 times in the
>>> function, I'd recommend:
>>>
>>> 	...
>>> 	u32 args_size;
>>>
>>> 	if (check_add_overflow(sizeof(*args), size, &args_size))
>>> 		return -ENOMEM;
>>> 	if (args_size > sizeof(stack)) {
>>> 		if (!(args = kmalloc(args_size, GFP_KERNEL)))
> 
> trivia:
> 
> More typical kernel style would use separate alloc and test
> 
> 		args = kmalloc(args_size, GFP_KERNEL);
> 		if (!args)
> 

Sure, I can do that as well. I'll wait a couple of days though before
sending v3 in case there are more change requests.

Guenter