[PATCH] drm/sysfb: ofdrm: Fix integer overflow in fb_size calculation

[PATCH] drm/sysfb: ofdrm: Fix integer overflow in fb_size calculation

[oushixiong1025]

From: Shixiong Ou <oushixiong@kylinos.cn>

The framebuffer size calculation `fb_size = linebytes * height` can
overflow when both values are large (e.g., 46341 * 46341 > INT_MAX).
Since linebytes and height are both int types, the multiplication is
performed as int * int, which results in undefined behavior on overflow.

Use check_mul_overflow() to detect and prevent this overflow, consistent
with the approach used in simpledrm.c and corebootdrm.c.

Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
---
 drivers/gpu/drm/sysfb/ofdrm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sysfb/ofdrm.c b/drivers/gpu/drm/sysfb/ofdrm.c
index 819aed466727..a6dc34b9ec0f 100644
--- a/drivers/gpu/drm/sysfb/ofdrm.c
+++ b/drivers/gpu/drm/sysfb/ofdrm.c
@@ -2,6 +2,7 @@
 
 #include <linux/aperture.h>
 #include <linux/of_address.h>
+#include <linux/overflow.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
@@ -913,7 +914,10 @@ static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
 			return ERR_PTR(-EINVAL);
 	}
 
-	fb_size = linebytes * height;
+	if (check_mul_overflow(linebytes, height, &fb_size)) {
+		drm_err(dev, "framebuffer size exceeds maximum\n");
+		return ERR_PTR(-EINVAL);
+	}
 
 	/*
 	 * Try to figure out the address of the framebuffer. Unfortunately, Open
-- 
2.25.1


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Re: [PATCH] drm/sysfb: ofdrm: Fix integer overflow in fb_size calculation

[Thomas Zimmermann]

Am 24.07.26 um 11:41 schrieb oushixiong1025@163.com:
> From: Shixiong Ou <oushixiong@kylinos.cn>
>
> The framebuffer size calculation `fb_size = linebytes * height` can
> overflow when both values are large (e.g., 46341 * 46341 > INT_MAX).
> Since linebytes and height are both int types, the multiplication is
> performed as int * int, which results in undefined behavior on overflow.
>
> Use check_mul_overflow() to detect and prevent this overflow, consistent
> with the approach used in simpledrm.c and corebootdrm.c.
>
> Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

Thanks for the fix.

> ---
>   drivers/gpu/drm/sysfb/ofdrm.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/sysfb/ofdrm.c b/drivers/gpu/drm/sysfb/ofdrm.c
> index 819aed466727..a6dc34b9ec0f 100644
> --- a/drivers/gpu/drm/sysfb/ofdrm.c
> +++ b/drivers/gpu/drm/sysfb/ofdrm.c
> @@ -2,6 +2,7 @@
>   
>   #include <linux/aperture.h>
>   #include <linux/of_address.h>
> +#include <linux/overflow.h>
>   #include <linux/pci.h>
>   #include <linux/platform_device.h>
>   #include <linux/pm.h>
> @@ -913,7 +914,10 @@ static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
>   			return ERR_PTR(-EINVAL);
>   	}
>   
> -	fb_size = linebytes * height;
> +	if (check_mul_overflow(linebytes, height, &fb_size)) {
> +		drm_err(dev, "framebuffer size exceeds maximum\n");
> +		return ERR_PTR(-EINVAL);
> +	}
>   
>   	/*
>   	 * Try to figure out the address of the framebuffer. Unfortunately, Open

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)