Merge branch 'akpm' (patches from Andrew)

Merge misc fixes from Andrew Morton:
 "2 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  hugetlbfs: fix races and page leaks during migration
  kasan: turn off asan-stack for clang-8 and earlier

fs/hugetlbfs/inode.c

@@ -859,6 +859,18 @@ static int hugetlbfs_migrate_page(struct address_space *mapping,
 	rc = migrate_huge_page_move_mapping(mapping, newpage, page);
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
+
+	/*
+	 * page_private is subpool pointer in hugetlb pages.  Transfer to
+	 * new page.  PagePrivate is not associated with page_private for
+	 * hugetlb pages and can not be set here as only page_huge_active
+	 * pages can be migrated.
+	 */
+	if (page_private(page)) {
+		set_page_private(newpage, page_private(page));
+		set_page_private(page, 0);
+	}
+
 	if (mode != MIGRATE_SYNC_NO_COPY)
 		migrate_page_copy(newpage, page);
 	else

lib/Kconfig.kasan

@@ -113,6 +113,28 @@ config KASAN_INLINE
 
 endchoice
 
+config KASAN_STACK_ENABLE
+	bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
+	default !(CLANG_VERSION < 90000)
+	depends on KASAN
+	help
+	  The LLVM stack address sanitizer has a know problem that
+	  causes excessive stack usage in a lot of functions, see
+	  https://bugs.llvm.org/show_bug.cgi?id=38809
+	  Disabling asan-stack makes it safe to run kernels build
+	  with clang-8 with KASAN enabled, though it loses some of
+	  the functionality.
+	  This feature is always disabled when compile-testing with clang-8
+	  or earlier to avoid cluttering the output in stack overflow
+	  warnings, but clang-8 users can still enable it for builds without
+	  CONFIG_COMPILE_TEST.  On gcc and later clang versions it is
+	  assumed to always be safe to use and enabled by default.
+
+config KASAN_STACK
+	int
+	default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
+	default 0
+
 config KASAN_S390_4_LEVEL_PAGING
 	bool "KASan: use 4-level paging"
 	depends on KASAN && S390

mm/hugetlb.c

@@ -3624,7 +3624,6 @@ retry_avoidcopy:
 	copy_user_huge_page(new_page, old_page, address, vma,
 			    pages_per_huge_page(h));
 	__SetPageUptodate(new_page);
-	set_page_huge_active(new_page);
 
 	mmu_notifier_range_init(&range, mm, haddr, haddr + huge_page_size(h));
 	mmu_notifier_invalidate_range_start(&range);
@@ -3645,6 +3644,7 @@ retry_avoidcopy:
 				make_huge_pte(vma, new_page, 1));
 		page_remove_rmap(old_page, true);
 		hugepage_add_new_anon_rmap(new_page, vma, haddr);
+		set_page_huge_active(new_page);
 		/* Make the old page be freed below */
 		new_page = old_page;
 	}
@@ -3729,6 +3729,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
 	pte_t new_pte;
 	spinlock_t *ptl;
 	unsigned long haddr = address & huge_page_mask(h);
+	bool new_page = false;
 
 	/*
 	 * Currently, we are forced to kill the process in the event the
@@ -3790,7 +3791,7 @@ retry:
 		}
 		clear_huge_page(page, address, pages_per_huge_page(h));
 		__SetPageUptodate(page);
-		set_page_huge_active(page);
+		new_page = true;
 
 		if (vma->vm_flags & VM_MAYSHARE) {
 			int err = huge_add_to_page_cache(page, mapping, idx);
@@ -3861,6 +3862,15 @@ retry:
 	}
 
 	spin_unlock(ptl);
+
+	/*
+	 * Only make newly allocated pages active.  Existing pages found
+	 * in the pagecache could be !page_huge_active() if they have been
+	 * isolated for migration.
+	 */
+	if (new_page)
+		set_page_huge_active(page);
+
 	unlock_page(page);
 out:
 	return ret;
@@ -4095,7 +4105,6 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
 	 * the set_pte_at() write.
 	 */
 	__SetPageUptodate(page);
-	set_page_huge_active(page);
 
 	mapping = dst_vma->vm_file->f_mapping;
 	idx = vma_hugecache_offset(h, dst_vma, dst_addr);
@@ -4163,6 +4172,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
 	update_mmu_cache(dst_vma, dst_addr, dst_pte);
 
 	spin_unlock(ptl);
+	set_page_huge_active(page);
 	if (vm_shared)
 		unlock_page(page);
 	ret = 0;

mm/migrate.c

@@ -1315,6 +1315,16 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 		lock_page(hpage);
 	}
 
+	/*
+	 * Check for pages which are in the process of being freed.  Without
+	 * page_mapping() set, hugetlbfs specific move page routine will not
+	 * be called and we could leak usage counts for subpools.
+	 */
+	if (page_private(hpage) && !page_mapping(hpage)) {
+		rc = -EBUSY;
+		goto out_unlock;
+	}
+
 	if (PageAnon(hpage))
 		anon_vma = page_get_anon_vma(hpage);
 
@@ -1345,6 +1355,7 @@ put_anon:
 		put_new_page = NULL;
 	}
 
+out_unlock:
 	unlock_page(hpage);
 out:
 	if (rc != -EAGAIN)

scripts/Makefile.kasan

@@ -26,7 +26,7 @@ else
 	CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
 	 $(call cc-param,asan-globals=1) \
 	 $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
-	 $(call cc-param,asan-stack=1) \
+	 $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
 	 $(call cc-param,asan-use-after-scope=1) \
 	 $(call cc-param,asan-instrument-allocas=1)
 endif