2023-02-22 15:57:48

by Tom Rix

[permalink] [raw]
Subject: [PATCH] drm/msm: return early when allocating fbdev fails

building with clang and W=1 reports
drivers/gpu/drm/msm/msm_fbdev.c:144:6: error: variable 'helper' is used
uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
if (!fbdev)
^~~~~~

helper is only initialized after fbdev succeeds, so is in a garbage state at
the fail: label. There is nothing to unwinded if fbdev alloaction fails,
return NULL.

Fixes: 3fb1f62f80a1 ("drm/fb-helper: Remove drm_fb_helper_unprepare() from drm_fb_helper_fini()")
Signed-off-by: Tom Rix <[email protected]>
---
drivers/gpu/drm/msm/msm_fbdev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
index c804e5ba682a..c1356aff87da 100644
--- a/drivers/gpu/drm/msm/msm_fbdev.c
+++ b/drivers/gpu/drm/msm/msm_fbdev.c
@@ -142,7 +142,7 @@ struct drm_fb_helper *msm_fbdev_init(struct drm_device *dev)

fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
if (!fbdev)
- goto fail;
+ return NULL;

helper = &fbdev->base;

--
2.27.0



2023-02-22 16:09:46

by Thomas Zimmermann

[permalink] [raw]
Subject: Re: [PATCH] drm/msm: return early when allocating fbdev fails

Hi

Am 22.02.23 um 16:56 schrieb Tom Rix:
> building with clang and W=1 reports
> drivers/gpu/drm/msm/msm_fbdev.c:144:6: error: variable 'helper' is used
> uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> if (!fbdev)
> ^~~~~~
>
> helper is only initialized after fbdev succeeds, so is in a garbage state at
> the fail: label. There is nothing to unwinded if fbdev alloaction fails,
> return NULL.
>
> Fixes: 3fb1f62f80a1 ("drm/fb-helper: Remove drm_fb_helper_unprepare() from drm_fb_helper_fini()")
> Signed-off-by: Tom Rix <[email protected]>

Already fixed here:
https://lore.kernel.org/dri-devel/[email protected]/T/#t

Best regards
Thomas

> ---
> drivers/gpu/drm/msm/msm_fbdev.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
> index c804e5ba682a..c1356aff87da 100644
> --- a/drivers/gpu/drm/msm/msm_fbdev.c
> +++ b/drivers/gpu/drm/msm/msm_fbdev.c
> @@ -142,7 +142,7 @@ struct drm_fb_helper *msm_fbdev_init(struct drm_device *dev)
>
> fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
> if (!fbdev)
> - goto fail;
> + return NULL;
>
> helper = &fbdev->base;
>

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev


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2023-02-22 18:21:36

by Nathan Chancellor

[permalink] [raw]
Subject: Re: [PATCH] drm/msm: return early when allocating fbdev fails

On Wed, Feb 22, 2023 at 05:09:40PM +0100, Thomas Zimmermann wrote:
> Hi
>
> Am 22.02.23 um 16:56 schrieb Tom Rix:
> > building with clang and W=1 reports
> > drivers/gpu/drm/msm/msm_fbdev.c:144:6: error: variable 'helper' is used
> > uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> > if (!fbdev)
> > ^~~~~~
> >
> > helper is only initialized after fbdev succeeds, so is in a garbage state at
> > the fail: label. There is nothing to unwinded if fbdev alloaction fails,
> > return NULL.
> >
> > Fixes: 3fb1f62f80a1 ("drm/fb-helper: Remove drm_fb_helper_unprepare() from drm_fb_helper_fini()")
> > Signed-off-by: Tom Rix <[email protected]>
>
> Already fixed here: https://lore.kernel.org/dri-devel/[email protected]/T/#t

There is also:

../drivers/gpu/drm/omapdrm/omap_fbdev.c:235:6: error: variable 'helper' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
if (!fbdev)
^~~~~~
../drivers/gpu/drm/omapdrm/omap_fbdev.c:259:26: note: uninitialized use occurs here
drm_fb_helper_unprepare(helper);
^~~~~~
../drivers/gpu/drm/omapdrm/omap_fbdev.c:235:2: note: remove the 'if' if its condition is always false
if (!fbdev)
^~~~~~~~~~~
../drivers/gpu/drm/omapdrm/omap_fbdev.c:228:30: note: initialize the variable 'helper' to silence this warning
struct drm_fb_helper *helper;
^
= NULL
1 error generated.

Is the fix the same as the one you have linked above?

Cheers,
Nathan