video: fbdev: pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write

mainline inclusion
from mainline-v5.19-rc4
commit a09d2d00
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5PRMO
CVE: CVE-2022-39842

---------------------

In pxa3xx_gcu_write, a count parameter of type size_t is passed to words of
type int.  Then, copy_from_user() may cause a heap overflow because it is used
as the third argument of copy_from_user().
Signed-off-by: NHyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: NHelge Deller <deller@gmx.de>
Signed-off-by: NZhao Wenhui <zhaowenhui8@huawei.com>
Reviewed-by: NChen Hui <judy.chenhui@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

drivers/video/fbdev/pxa3xx-gcu.c

@@ -394,7 +394,7 @@ pxa3xx_gcu_write(struct file *file, const char *buff,
 	struct pxa3xx_gcu_batch	*buffer;
 	struct pxa3xx_gcu_priv *priv = to_pxa3xx_gcu_priv(file);
 
-	int words = count / 4;
+	size_t words = count / 4;
 
 	/* Does not need to be atomic. There's a lock in user space,
 	 * but anyhow, this is just for statistics. */