lightnvm: fix out-of-bounds write to array devices->info[]

There is an off-by-one array check that can lead to a out-of-bounds
write to devices->info[i].  Fix this by checking by using >= rather
than > for the size check. Also replace hard-coded array size limit
with ARRAY_SIZE on the array.

Addresses-Coverity: ("Out-of-bounds write")
Fixes: cd9e980 ("lightnvm: Support for Open-Channel SSDs")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Colin Ian King

drivers/lightnvm/core.c

@@ -1311,8 +1311,9 @@ static long nvm_ioctl_get_devices(struct file *file, void __user *arg)
 		strlcpy(info->bmname, "gennvm", sizeof(info->bmname));
 		i++;
 
-		if (i > 31) {
-			pr_err("max 31 devices can be reported.\n");
+		if (i >= ARRAY_SIZE(devices->info)) {
+			pr_err("max %zd devices can be reported.\n",
+			       ARRAY_SIZE(devices->info));
 			break;
 		}
 	}