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: Andi Kleen <ak@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 66e1c51be084..5f793e6c854b 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/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)