Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 MPX fixes from Thomas Gleixner:
 "Three updates for the new MPX infrastructure:
   - Use the proper error check in the trap handler
   - Add a proper config option for it
   - Bring documentation up to date"

* 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, mpx: Give MPX a real config option prompt
  x86, mpx: Update documentation
  x86_64/traps: Fix always true condition

2 files changed, 27 insertions, 5 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d69f1cd..2995788 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -249,10 +249,6 @@ config HAVE_INTEL_TXT
 	def_bool y
 	depends on INTEL_IOMMU && ACPI
 
-config X86_INTEL_MPX
-	def_bool y
-	depends on CPU_SUP_INTEL
-
 config X86_32_SMP
 	def_bool y
 	depends on X86_32 && SMP
@@ -1594,6 +1590,32 @@ config X86_SMAP
 
 	  If unsure, say Y.
 
+config X86_INTEL_MPX
+	prompt "Intel MPX (Memory Protection Extensions)"
+	def_bool n
+	depends on CPU_SUP_INTEL
+	---help---
+	  MPX provides hardware features that can be used in
+	  conjunction with compiler-instrumented code to check
+	  memory references.  It is designed to detect buffer
+	  overflow or underflow bugs.
+
+	  This option enables running applications which are
+	  instrumented or otherwise use MPX.  It does not use MPX
+	  itself inside the kernel or to protect the kernel
+	  against bad memory references.
+
+	  Enabling this option will make the kernel larger:
+	  ~8k of kernel text and 36 bytes of data on a 64-bit
+	  defconfig.  It adds a long to the 'mm_struct' which
+	  will increase the kernel memory overhead of each
+	  process and adds some branches to paths used during
+	  exec() and munmap().
+
+	  For details, see Documentation/x86/intel_mpx.txt
+
+	  If unsure, say N.
+
 config EFI
 	bool "EFI runtime service support"
 	depends on ACPI
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index a9ae205..88900e2 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -331,7 +331,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
 		break; /* Success, it was handled */
 	case 1: /* Bound violation. */
 		info = mpx_generate_siginfo(regs, xsave_buf);
-		if (PTR_ERR(info)) {
+		if (IS_ERR(info)) {
 			/*
 			 * We failed to decode the MPX instruction.  Act as if
 			 * the exception was not caused by MPX.