2 files changed, 17 insertions, 4 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4e7fb9c3bfa5..cdf79ab628c2 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1570,9 +1570,13 @@ void cpu_init(void)
         initialize_tlbstate_and_flush();
         enter_lazy_tlb(&init_mm, me);
 
-        load_sp0(current->thread.sp0);
+        /*
+         * Initialize the TSS.  Don't bother initializing sp0, as the initial
+         * task never enters user mode.
+         */
         set_tss_desc(cpu, t);
         load_TR_desc();
+
         load_mm_ldt(&init_mm);
 
         clear_all_debug_regs();
@@ -1594,7 +1598,6 @@ void cpu_init(void)
         int cpu = smp_processor_id();
         struct task_struct *curr = current;
         struct tss_struct *t = &per_cpu(cpu_tss, cpu);
-        struct thread_struct *thread = &curr->thread;
 
         wait_for_master_cpu(cpu);
 
@@ -1625,9 +1628,13 @@ void cpu_init(void)
         initialize_tlbstate_and_flush();
         enter_lazy_tlb(&init_mm, curr);
 
-        load_sp0(thread->sp0);
+        /*
+         * Initialize the TSS.  Don't bother initializing sp0, as the initial
+         * task never enters user mode.
+         */
         set_tss_desc(cpu, t);
         load_TR_desc();
+
         load_mm_ldt(&init_mm);
 
         t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index bd6b85fac666..ff8a9acbcf8b 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -48,7 +48,13 @@
  */
 __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
         .x86_tss = {
-                .sp0 = TOP_OF_INIT_STACK,
+                /*
+                 * .sp0 is only used when entering ring 0 from a lower
+                 * privilege level.  Since the init task never runs anything
+                 * but ring 0 code, there is no need for a valid value here.
+                 * Poison it.
+                 */
+                .sp0 = (1UL << (BITS_PER_LONG-1)) + 1,
 #ifdef CONFIG_X86_32
                 .ss0 = __KERNEL_DS,
                 .ss1 = __KERNEL_CS,