efi/libstub: Don't parse overlong command lines

#include <stdarg.h>

#include <linux/ctype.h>

#include <linux/efi.h>

#include <linux/kernel.h>

#include <linux/printk.h> /* For CONSOLE_LOGLEVEL_* */

#include <asm/efi.h>

#include <asm/setup.h>

#include "efistub.h"

	unsigned long cmdline_addr = 0;

	int options_chars = efi_table_attr(image, load_options_size) / 2;

	const u16 *options = efi_table_attr(image, load_options);

	int options_bytes = 0;  /* UTF-8 bytes */

	int options_bytes = 0, safe_options_bytes = 0;  /* UTF-8 bytes */

	bool in_quote = false;

	efi_status_t status;

	if (options) {

		s2 = options;

		while (options_chars--) {

		while (options_bytes < COMMAND_LINE_SIZE && options_chars--) {

			u16 c = *s2++;

			if (c < 0x80) {

				if (c == L'\0' || c == L'\n')

					break;

				if (c == L'"')

					in_quote = !in_quote;

				else if (!in_quote && isspace((char)c))

					safe_options_bytes = options_bytes;

				options_bytes++;

				continue;

			}

			/*

			 * Get the number of UTF-8 bytes corresponding to a

			 * UTF-16 character.

			 * The first part handles everything in the BMP.

			 */

			options_bytes += 1 + (c >= 0x80) + (c >= 0x800);

			options_bytes += 2 + (c >= 0x800);

			/*

			 * Add one more byte for valid surrogate pairs. Invalid

			 * surrogates will be replaced with 0xfffd and take up

				}

			}

		}

		if (options_bytes >= COMMAND_LINE_SIZE) {

			options_bytes = safe_options_bytes;

			efi_err("Command line is too long: truncated to %d bytes\n",

				options_bytes);

		}

	}

	options_bytes++;	/* NUL termination */