linux-kernel - Re: [PATCH] drm/nouveau: usif_ioctl: ensure returns are initialized

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Date:	Wed, 1 Jul 2015 12:56:37 -0400
From:	Ilia Mirkin <imirkin@...m.mit.edu>
To:	Colin King <colin.king@...onical.com>
Cc:	David Airlie <airlied@...ux.ie>, Ben Skeggs <bskeggs@...hat.com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/nouveau: usif_ioctl: ensure returns are initialized

On Wed, Jul 1, 2015 at 12:51 PM, Colin King <colin.king@...onical.com> wrote:
> From: Colin Ian King <colin.king@...onical.com>
>
> Various usif_ioctl helper functions do not initialize the
> return variable ret and some of the error handling return
> paths just return garbage values that were on the stack (or
> in a register).  I believe that in all the cases, the
> initial ret variable should be set to -EINVAL and subsequent
> paths through these helper functions set it appropriately
> otherwise.
>
> Found via static analysis using cppcheck:
>
> [drivers/gpu/drm/nouveau/nouveau_usif.c:138]:
>     (error) Uninitialized variable: ret

It sure would seem that way, wouldn't it?

#define nvif_unpack(d,vl,vh,m) ({                                              \
        if ((vl) == 0 || ret == -ENOSYS) {                                     \
                int _size = sizeof(d);                                         \
                if (_size <= size && (d).version >= (vl) &&                    \
                                     (d).version <= (vh)) {                    \
                        data = (u8 *)data + _size;                             \
                        size = size - _size;                                   \
                        ret = ((m) || !size) ? 0 : -E2BIG;                     \
                } else {                                                       \
                        ret = -ENOSYS;                                         \
                }                                                              \
        }                                                                      \
        (ret == 0);                                                            \
})

So actually it does get initialized, and I guess cppcheck doesn't know
about macros?

> [drivers/gpu/drm/nouveau/nouveau_usif.c:179]:
>     (error) Uninitialized variable: ret
> [drivers/gpu/drm/nouveau/nouveau_usif.c:202]:
>     (error) Uninitialized variable: ret
> [drivers/gpu/drm/nouveau/nouveau_usif.c:241]:
>     (error) Uninitialized variable: ret
> [drivers/gpu/drm/nouveau/nouveau_usif.c:157]:
>     (error) Uninitialized variable: ret
> [drivers/gpu/drm/nouveau/nouveau_usif.c:288]:
>     (error) Uninitialized variable: ret
>
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_usif.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_usif.c b/drivers/gpu/drm/nouveau/nouveau_usif.c
> index cb1182d..01b50a2 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_usif.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_usif.c
> @@ -129,7 +129,7 @@ usif_notify_new(struct drm_file *f, void *data, u32 size, void *argv, u32 argc)
>                 struct nvif_notify_req_v0 v0;
>         } *req;
>         struct usif_notify *ntfy;
> -       int ret;
> +       int ret = -EINVAL;
>
>         if (nvif_unpack(args->v0, 0, 0, true)) {
>                 if (usif_notify_find(f, args->v0.index))
> @@ -170,7 +170,7 @@ usif_notify_del(struct drm_file *f, void *data, u32 size, void *argv, u32 argc)
>                 struct nvif_ioctl_ntfy_del_v0 v0;
>         } *args = data;
>         struct usif_notify *ntfy;
> -       int ret;
> +       int ret = -EINVAL;
>
>         if (nvif_unpack(args->v0, 0, 0, true)) {
>                 if (!(ntfy = usif_notify_find(f, args->v0.index)))
> @@ -193,7 +193,7 @@ usif_notify_get(struct drm_file *f, void *data, u32 size, void *argv, u32 argc)
>                 struct nvif_ioctl_ntfy_del_v0 v0;
>         } *args = data;
>         struct usif_notify *ntfy;
> -       int ret;
> +       int ret = -EINVAL;
>
>         if (nvif_unpack(args->v0, 0, 0, true)) {
>                 if (!(ntfy = usif_notify_find(f, args->v0.index)))
> @@ -232,7 +232,7 @@ usif_notify_put(struct drm_file *f, void *data, u32 size, void *argv, u32 argc)
>                 struct nvif_ioctl_ntfy_put_v0 v0;
>         } *args = data;
>         struct usif_notify *ntfy;
> -       int ret;
> +       int ret = -EINVAL;
>
>         if (nvif_unpack(args->v0, 0, 0, true)) {
>                 if (!(ntfy = usif_notify_find(f, args->v0.index)))
> @@ -269,7 +269,7 @@ usif_object_new(struct drm_file *f, void *data, u32 size, void *argv, u32 argc)
>                 struct nvif_ioctl_new_v0 v0;
>         } *args = data;
>         struct usif_object *object;
> -       int ret;
> +       int ret = -EINVAL;
>
>         if (!(object = kmalloc(sizeof(*object), GFP_KERNEL)))
>                 return -ENOMEM;
> --
> 2.1.4
>
> --
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