MCE: Fix vm86 handling for 32bit mce handler

When running on 32bit the mce handler could misinterpret
vm86 mode as ring 0. This can affect whether it does recovery
or not; it was possible to panic when recovery was actually
possible.

Fix this by always forcing vm86 to look like ring 3.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NTony Luck <tony.luck@intel.com>

arch/x86/kernel/cpu/mcheck/mce.c

@@ -437,6 +437,14 @@ static inline void mce_gather_info(struct mce *m, struct pt_regs *regs)
 		if (m->mcgstatus & (MCG_STATUS_RIPV|MCG_STATUS_EIPV)) {
 			m->ip = regs->ip;
 			m->cs = regs->cs;
+
+			/*
+			 * When in VM86 mode make the cs look like ring 3
+			 * always. This is a lie, but it's better than passing
+			 * the additional vm86 bit around everywhere.
+			 */
+			if (v8086_mode(regs))
+				m->cs |= 3;
 		}
 		/* Use accurate RIP reporting if available. */
 		if (rip_msr)