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

Pull core fixes from Ingo Molnar:
"This fixes a particularly thorny munmap() bug with MPX, plus fixes a
host build environment assumption in objtool"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool: Allow AR to be overridden with HOSTAR
x86/mpx, mm/core: Fix recursive munmap() corruption

arch/powerpc/include/asm/mmu_context.h

···
 extern void arch_exit_mmap(struct mm_struct *mm);
 
 static inline void arch_unmap(struct mm_struct *mm,
-			      struct vm_area_struct *vma,
 			      unsigned long start, unsigned long end)
 {
 	if (start <= mm->context.vdso_base && mm->context.vdso_base < end)

arch/um/include/asm/mmu_context.h

···
 }
 extern void arch_exit_mmap(struct mm_struct *mm);
 static inline void arch_unmap(struct mm_struct *mm,
-			struct vm_area_struct *vma,
 			unsigned long start, unsigned long end)
 {
 }

arch/unicore32/include/asm/mmu_context.h

···
 }
 
 static inline void arch_unmap(struct mm_struct *mm,
-			struct vm_area_struct *vma,
 			unsigned long start, unsigned long end)
 {
 }

arch/x86/include/asm/mmu_context.h

···
 	mpx_mm_init(mm);
 }
 
-static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
-			      unsigned long start, unsigned long end)
+static inline void arch_unmap(struct mm_struct *mm, unsigned long start,
+			      unsigned long end)
 {
 	/*
 	 * mpx_notify_unmap() goes and reads a rarely-hot
···
 	 * consistently wrong.
 	 */
 	if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX)))
-		mpx_notify_unmap(mm, vma, start, end);
+		mpx_notify_unmap(mm, start, end);
 }
 
 /*

arch/x86/include/asm/mpx.h

···
 };
 
 #ifdef CONFIG_X86_INTEL_MPX
-int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs);
-int mpx_handle_bd_fault(void);
+
+extern int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs);
+extern int mpx_handle_bd_fault(void);
+
 static inline int kernel_managing_mpx_tables(struct mm_struct *mm)
 {
 	return (mm->context.bd_addr != MPX_INVALID_BOUNDS_DIR);
 }
+
 static inline void mpx_mm_init(struct mm_struct *mm)
 {
 	/*
···
 	 */
 	mm->context.bd_addr = MPX_INVALID_BOUNDS_DIR;
 }
-void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
-		      unsigned long start, unsigned long end);
 
-unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len,
-		unsigned long flags);
+extern void mpx_notify_unmap(struct mm_struct *mm, unsigned long start, unsigned long end);
+extern unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len, unsigned long flags);
+
 #else
 static inline int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs)
 {
···
 {
 }
 static inline void mpx_notify_unmap(struct mm_struct *mm,
-				    struct vm_area_struct *vma,
 				    unsigned long start, unsigned long end)
 {
 }

arch/x86/mm/mpx.c

···
  * the virtual address region start...end have already been split if
  * necessary, and the 'vma' is the first vma in this range (start -> end).
  */
-void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
-		unsigned long start, unsigned long end)
+void mpx_notify_unmap(struct mm_struct *mm, unsigned long start,
+		      unsigned long end)
 {
+	struct vm_area_struct *vma;
 	int ret;
 
 	/*
···
 	 * which should not occur normally. Being strict about it here
 	 * helps ensure that we do not have an exploitable stack overflow.
 	 */
-	do {
+	vma = find_vma(mm, start);
+	while (vma && vma->vm_start < end) {
 		if (vma->vm_flags & VM_MPX)
 			return;
 		vma = vma->vm_next;
-	} while (vma && vma->vm_start < end);
+	}
 
 	ret = mpx_unmap_tables(mm, start, end);
 	if (ret)

include/asm-generic/mm_hooks.h

···
 }
 
 static inline void arch_unmap(struct mm_struct *mm,
-			struct vm_area_struct *vma,
 			unsigned long start, unsigned long end)
 {
 }

mm/mmap.c

···
 		return -EINVAL;
 
 	len = PAGE_ALIGN(len);
+	end = start + len;
 	if (len == 0)
 		return -EINVAL;
+
+	/*
+	 * arch_unmap() might do unmaps itself.  It must be called
+	 * and finish any rbtree manipulation before this code
+	 * runs and also starts to manipulate the rbtree.
+	 */
+	arch_unmap(mm, start, end);
 
 	/* Find the first overlapping VMA */
 	vma = find_vma(mm, start);
···
 	/* we have  start < vma->vm_end  */
 
 	/* if it doesn't overlap, we have nothing.. */
-	end = start + len;
 	if (vma->vm_start >= end)
 		return 0;
 
···
 
 	/* Detach vmas from rbtree */
 	detach_vmas_to_be_unmapped(mm, vma, prev, end);
-
-	/*
-	 * mpx unmap needs to be called with mmap_sem held for write.
-	 * It is safe to call it before unmap_region().
-	 */
-	arch_unmap(mm, vma, start, end);
 
 	if (downgrade)
 		downgrade_write(&mm->mmap_sem);

tools/objtool/Makefile

···
 endif
 
 # always use the host compiler
+HOSTAR	?= ar
 HOSTCC	?= gcc
 HOSTLD	?= ld
+AR	 = $(HOSTAR)
 CC	 = $(HOSTCC)
 LD	 = $(HOSTLD)
-AR	 = ar
 
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))