[PATCH] mpparse: prevent table index out-of-bounds

John Z. Bohach <jzb@aexorsyst.com> found this bug:

  If the board has more than 32 PCI busses on it, the mptable bus array will
  overwrite its bounds for the PCI busses, and stomp on anything that's after
  it.

Prevent possible table overflow and unknown data corruption.  Code is in an
__init section so it will be discarded after init.
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/mpparse.c

@@ -229,6 +229,13 @@ static void __init MP_bus_info (struct mpc_config_bus *m)
 
 	mpc_oem_bus_info(m, str, translation_table[mpc_record]);
 
+	if (m->mpc_busid >= MAX_MP_BUSSES) {
+		printk(KERN_WARNING "MP table busid value (%d) for bustype %s "
+			" is too large, max. supported is %d\n",
+			m->mpc_busid, str, MAX_MP_BUSSES - 1);
+		return;
+	}
+
 	if (strncmp(str, BUSTYPE_ISA, sizeof(BUSTYPE_ISA)-1) == 0) {
 		mp_bus_id_to_type[m->mpc_busid] = MP_BUS_ISA;
 	} else if (strncmp(str, BUSTYPE_EISA, sizeof(BUSTYPE_EISA)-1) == 0) {