Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/l…

…inux/kernel/git/tip/tip

Pull x86 fix from Ingo Molnar:
 "This contains a single TLS ABI validation fix from Andy Lutomirski"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/tls: Don't validate lm in set_thread_area() after all

arch/x86/include/uapi/asm/ldt.h

@@ -28,6 +28,13 @@ struct user_desc {
 	unsigned int  seg_not_present:1;
 	unsigned int  useable:1;
 #ifdef __x86_64__
+	/*
+	 * Because this bit is not present in 32-bit user code, user
+	 * programs can pass uninitialized values here.  Therefore, in
+	 * any context in which a user_desc comes from a 32-bit program,
+	 * the kernel must act as though lm == 0, regardless of the
+	 * actual value.
+	 */
 	unsigned int  lm:1;
 #endif
 };

arch/x86/kernel/tls.c

@@ -55,12 +55,6 @@ static bool tls_desc_okay(const struct user_desc *info)
 	if (info->seg_not_present)
 		return false;
 
-#ifdef CONFIG_X86_64
-	/* The L bit makes no sense for data. */
-	if (info->lm)
-		return false;
-#endif
-
 	return true;
 }