| From | Greg Kroah-Hartman <> | Subject | [ 126/127] MCE: Fix vm86 handling for 32bit mce handler | Date | Fri, 28 Sep 2012 13:34:59 -0700 |
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3.0-stable review patch. If anyone has any objections, please let me know.
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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>
--- arch/x86/kernel/cpu/mcheck/mce.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -451,6 +451,13 @@ static inline void mce_get_rip(struct mc 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; @@ -988,6 +995,7 @@ void do_machine_check(struct pt_regs *re */ add_taint(TAINT_MACHINE_CHECK); + mce_get_rip(&m, regs); severity = mce_severity(&m, tolerant, NULL); /* @@ -1026,7 +1034,6 @@ void do_machine_check(struct pt_regs *re 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) {
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