# \[PATCH AUTOSEL 4.14 083/115\] fbdev: sbuslib: integer overflow in sbusfb\_ioctl\_helper()

- From: Sasha Levin \<sashal@kernel.org\>
- Date: 2019-11-13 01:58:49 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2019/11/5774842
- Thread: https://ratatoskr.run/stable/2019/11/5774806/t.md

```text
From: Dan Carpenter <redacted>

[ Upstream commit e5017716adb8aa5c01c52386c1b7470101ffe9c5 ]

The "index + count" addition can overflow.  Both come directly from the
user.  This bug leads to an information leak.

Signed-off-by: Dan Carpenter <redacted>
Cc: Peter Malone <redacted>
Cc: Philippe Ombredanne <redacted>
Cc: Mathieu Malaterre <redacted>
Signed-off-by: Bartlomiej Zolnierkiewicz <redacted>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/video/fbdev/sbuslib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
index 90c51330969c2..01a7110e61a76 100644
--- a/drivers/video/fbdev/sbuslib.c
+++ b/drivers/video/fbdev/sbuslib.c
@@ -171,7 +171,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
 		    get_user(ublue, &c->blue))
 			return -EFAULT;
 
-		if (index + count > cmap->len)
+		if (index > cmap->len || count > cmap->len - index)
 			return -EINVAL;
 
 		for (i = 0; i < count; i++) {
-- 
2.20.1
```