sm501: unsigned ptr cannot be negative

unsigned ptr cannot be negative
Signed-off-by: NRoel Kluin <roel.kluin@gmail.com>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/sm501fb.c

@@ -159,6 +159,9 @@ static int sm501_alloc_mem(struct sm501fb_info *inf, struct sm501_mem *mem,
 		break;
 
 	case SM501_MEMF_PANEL:
+		if (size > inf->fbmem_len)
+			return -ENOMEM;
+
 		ptr = inf->fbmem_len - size;
 		fbi = inf->fb[HEAD_CRT];
 
@@ -172,9 +175,6 @@ static int sm501_alloc_mem(struct sm501fb_info *inf, struct sm501_mem *mem,
 		if (fbi && ptr < fbi->fix.smem_len)
 			return -ENOMEM;
 
-		if (ptr < 0)
-			return -ENOMEM;
-
 		break;
 
 	case SM501_MEMF_CRT: