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Subject[ 059/184] MCE: Fix vm86 handling for 32bit mce handler
2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Andi Kleen <andi@firstfloor.org>

commit a129a7c84582629741e5fa6f40026efcd7a65bd4 upstream.

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.

[ Backport to 3.0 notes:
Things changed there slightly:
- move mce_get_rip() up. It fills up m->cs and m->ip values which
are evaluated in mce_severity(). Therefore move it up right before
the mce_severity call. This seem to be another bug in 3.0?
- Place the backport (fix m->cs in V86 case) to where m->cs gets
filled which is mce_get_rip() in 3.0
]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
arch/x86/kernel/cpu/mcheck/mce.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 0f16a2b..28a7e4c8 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -431,6 +431,13 @@ static inline void mce_get_rip(struct mce *m, struct pt_regs *regs)
if (regs && (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;
} else {
m->ip = 0;
m->cs = 0;
@@ -968,6 +975,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
*/
add_taint(TAINT_MACHINE_CHECK);

+ mce_get_rip(&m, regs);
severity = mce_severity(&m, tolerant, NULL);

/*
@@ -1006,7 +1014,6 @@ void do_machine_check(struct pt_regs *regs, long error_code)
if (severity == MCE_AO_SEVERITY && mce_usable_address(&m))
mce_ring_add(m.addr >> PAGE_SHIFT);

- mce_get_rip(&m, regs);
mce_log(&m);

if (severity > worst) {
--
1.7.12.2.21.g234cd45.dirty




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