[PATCH v1] drm/nouveau/clk: avoid potential null-dereference

[Vince Hsu]

On 01/08/2015 12:57 PM, Ilia Mirkin wrote:
> On Wed, Jan 7, 2015 at 11:32 PM, Vince Hsu <vinceh at nvidia.com> wrote:
>> On 01/08/2015 10:45 AM, Ilia Mirkin wrote:
>>> On Wed, Jan 7, 2015 at 5:29 PM, Andy Shevchenko
>>> <andy.shevchenko at gmail.com> wrote:
>>>> We have to check pointer before usage.
>>>>
>>>> Reported-by: Andrey Karpov <karpov at viva64.com>
>>>> Signed-off-by: Andy Shevchenko <andy.shevchenko at gmail.com>
>>>> ---
>>>>    drivers/gpu/drm/nouveau/core/subdev/clock/base.c | 4 +++-
>>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/nouveau/core/subdev/clock/base.c
>>>> b/drivers/gpu/drm/nouveau/core/subdev/clock/base.c
>>>> index e51b72d..2e84436 100644
>>>> --- a/drivers/gpu/drm/nouveau/core/subdev/clock/base.c
>>>> +++ b/drivers/gpu/drm/nouveau/core/subdev/clock/base.c
>>>> @@ -322,7 +322,6 @@ nouveau_pstate_new(struct nouveau_clock *clk, int
>>>> idx)
>>>>                   return 0;
>>>>
>>>>           pstate = kzalloc(sizeof(*pstate), GFP_KERNEL);
>>>> -       cstate = &pstate->base;
>>> What's wrong with this line? If pstate == NULL, &pstate->base == NULL
>>> as well and we return.
>> If pstate == NULL (kzalloc returned NULL), pstate->base triggers a null
>> pointer
>> deference error?
> Where do you see "pstate->base"? I only see "&pstate->base" which
> merely computes an offset into a structure... No reason to dereference
> pstate.
Sorry that I don't quite understand. We do need deference pstate to get
the member base which has type nouveau_cstate, and then assign
the address of base to cstate for later use.

struct nouveau_pstate {
     struct list_head head;
     struct list_head list; /* c-states */
     struct nouveau_cstate base;
     u8 pstate;
     u8 fanspeed;
};

Thanks,
Vince





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