x86/sev: Fix stack type check in vc_switch_off_ist()

The value of STACK_TYPE_EXCEPTION_LAST points to the last _valid_
exception stack. Reflect that in the check done in the
vc_switch_off_ist() function.

Fixes: a13644f3a53de ("x86/entry/64: Add entry code for #VC handler")
Reported-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021080833.30875-2-joro@8bytes.org

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index a58800973aed3a16cbb8d97500bae51eb8306716..f516f2b4797e62c753e00857f625afb9bf0636eb 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -709,7 +709,7 @@ asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *r
        stack = (unsigned long *)sp;
 
        if (!get_stack_info_noinstr(stack, current, &info) || info.type == STACK_TYPE_ENTRY ||
-           info.type >= STACK_TYPE_EXCEPTION_LAST)
+           info.type > STACK_TYPE_EXCEPTION_LAST)
                sp = __this_cpu_ist_top_va(VC2);
 
 sync: