# \[PATCH\] video: fbdev: vermilion: use 64-bit arithmetic instead of 32-bit

- Subsystems: FRAMEBUFFER LAYER, THE REST
- Maintainers: Helge Deller, Linus Torvalds
- List: linux-fbdev
- 2 messages, 2 authors
- Page: https://ratatoskr.run/linux-fbdev/2018/02/5204308/t

## \[PATCH\] video: fbdev: vermilion: use 64-bit arithmetic instead of 32-bit

- From: Gustavo A. R. Silva \<hidden\>
- Date: 2018-02-07 00:04:27 
- Message: https://ratatoskr.run/linux-fbdev/2018/02/5204308.md

```text
Cast _pitch_ to u64 in order to give the compiler complete information
about the proper arithmetic to use. Notice that this variable is
being used in a context that expects an expression of type u64
(64 bits, unsigned).

The expression pitch * var->yres_virtual is currently being evaluated
using 32-bit arithmetic and the result of the operation is being stored
into variable mem, which is a variable of type u64. Based on that,
chances are there is a potential integer overflow as a result of the
operation.

Addresses-Coverity-ID: 200655 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <redacted>
---
 drivers/video/fbdev/vermilion/vermilion.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/vermilion/vermilion.c b/drivers/video/fbdev/vermilion/vermilion.c
index 6f8d444..5172fa5 100644
--- a/drivers/video/fbdev/vermilion/vermilion.c
+++ b/drivers/video/fbdev/vermilion/vermilion.c
@@ -651,7 +651,7 @@ static int vmlfb_check_var_locked(struct fb_var_screeninfo *var,
 	}
 
 	pitch = ALIGN((var->xres * var->bits_per_pixel) >> 3, 0x40);
-	mem = pitch * var->yres_virtual;
+	mem = (u64)pitch * var->yres_virtual;
 	if (mem > vinfo->vram_contig_size) {
 		return -ENOMEM;
 	}
-- 
2.7.4

```

## Re: \[PATCH\] video: fbdev: vermilion: use 64-bit arithmetic instead of 32-bit

- From: Bartlomiej Zolnierkiewicz \<hidden\>
- Date: 2018-03-12 15:58:50 
- Message: https://ratatoskr.run/linux-fbdev/2018/03/5235002.md

```text
On Tuesday, February 06, 2018 06:04:24 PM Gustavo A. R. Silva wrote:
> Cast _pitch_ to u64 in order to give the compiler complete information
> about the proper arithmetic to use. Notice that this variable is
> being used in a context that expects an expression of type u64
> (64 bits, unsigned).
> 
> The expression pitch * var->yres_virtual is currently being evaluated
> using 32-bit arithmetic and the result of the operation is being stored
> into variable mem, which is a variable of type u64. Based on that,
> chances are there is a potential integer overflow as a result of the
> operation.
> 
> Addresses-Coverity-ID: 200655 ("Unintentional integer overflow")
> Signed-off-by: Gustavo A. R. Silva <redacted>

Patch queued for 4.17, thanks.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

```