x86/tls: Synchronize segment registers in set_thread_area()

[deliverable/linux.git] / arch / x86 / kernel / tls.c

diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c
index 7fc5e843f247b358288b23e459eebfefcf6631f0..9692a5e9fdab2002f31c6dd2dce2c113647608b6 100644 (file)
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -114,6 +114,7 @@ int do_set_thread_area(struct task_struct *p, int idx,
                       int can_allocate)
 {
        struct user_desc info;
+       unsigned short __maybe_unused sel, modified_sel;
 
        if (copy_from_user(&info, u_info, sizeof(info)))
                return -EFAULT;
@@ -141,6 +142,47 @@ int do_set_thread_area(struct task_struct *p, int idx,
 
        set_tls_desc(p, idx, &info, 1);
 
+       /*
+        * If DS, ES, FS, or GS points to the modified segment, forcibly
+        * refresh it.  Only needed on x86_64 because x86_32 reloads them
+        * on return to user mode.
+        */
+       modified_sel = (idx << 3) | 3;
+
+       if (p == current) {
+#ifdef CONFIG_X86_64
+               savesegment(ds, sel);
+               if (sel == modified_sel)
+                       loadsegment(ds, sel);
+
+               savesegment(es, sel);
+               if (sel == modified_sel)
+                       loadsegment(es, sel);
+
+               savesegment(fs, sel);
+               if (sel == modified_sel)
+                       loadsegment(fs, sel);
+
+               savesegment(gs, sel);
+               if (sel == modified_sel)
+                       load_gs_index(sel);
+#endif
+
+#ifdef CONFIG_X86_32_LAZY_GS
+               savesegment(gs, sel);
+               if (sel == modified_sel)
+                       loadsegment(gs, sel);
+#endif
+       } else {
+#ifdef CONFIG_X86_64
+               if (p->thread.fsindex == modified_sel)
+                       p->thread.fsbase = info.base_addr;
+
+               if (p->thread.gsindex == modified_sel)
+                       p->thread.gsbase = info.base_addr;
+#endif
+       }
+
        return 0;
 }