fbdev: sisfb: Fix strbuf array overflow

[ Upstream commit 9cf14f5a2746c19455ce9cb44341b5527b5e19c3 ]

The values of the variables xres and yres are placed in strbuf.
These variables are obtained from strbuf1.
The strbuf1 array contains digit characters
and a space if the array contains non-digit characters.
Then, when executing sprintf(strbuf, "%ux%ux8", xres, yres);
more than 16 bytes will be written to strbuf.
It is suggested to increase the size of the strbuf array to 24.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Andrey Shumilin <shum.sdl@nppct.ru>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/video/fbdev/sis/sis_main.c

@@ -184,7 +184,7 @@ static void sisfb_search_mode(char *name, bool quiet)
 {
 	unsigned int j = 0, xres = 0, yres = 0, depth = 0, rate = 0;
 	int i = 0;
-	char strbuf[16], strbuf1[20];
+	char strbuf[24], strbuf1[20];
 	char *nameptr = name;
 
 	/* We don't know the hardware specs yet and there is no ivideo */