1 files changed, 5 insertions, 3 deletions

diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index 9b4d51d0c0d0..0ccb53a9fcd9 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -5,6 +5,7 @@
 #include <linux/mm.h>
 #include <linux/ptrace.h>
 #include <asm/desc.h>
+#include <asm/mmu_context.h>
 
 unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs)
 {
@@ -27,13 +28,14 @@ unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *re
                 struct desc_struct *desc;
                 unsigned long base;
 
-                seg &= ~7UL;
+                seg >>= 3;
 
                 mutex_lock(&child->mm->context.lock);
-                if (unlikely((seg >> 3) >= child->mm->context.size))
+                if (unlikely(!child->mm->context.ldt ||
+                             seg >= child->mm->context.ldt->size))
                         addr = -1L; /* bogus selector, access would fault */
                 else {
-                        desc = child->mm->context.ldt + seg;
+                        desc = &child->mm->context.ldt->entries[seg];
                         base = get_desc_base(desc);
 
                         /* 16-bit code segment? */