From b06275e65f012db0ea85c65bc4e30fb9b7197cf8 Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Sun, 16 Aug 2015 12:54:41 +0200
Subject: vm: fix locking issues

Avoid accessing fields of `vm_object' objects without having it
locked.  These problems have been found using a code transformation
done by Coccinelle that instrumented all accesses with a runtime
check, and manual inspection.

* vm/memory_object.c (memory_object_data_supply): Avoid accessing
fields without the lock.
* vm/vm_fault.c (vm_fault_page): Likewise.
* vm/vm_map.c (vm_map_submap): Properly lock `object'.
(vm_map_copy_overwrite): Avoid accessing fields without the lock.
(vm_map_copyin): Lock `src_object'.
* vm/vm_object.c (_vm_object_setup): Likewise.
(vm_object_allocate): Likewise.
(vm_object_terminate): Avoid accessing fields without the lock.
(vm_object_copy_slowly): Lock `new_object'.
(vm_object_copy_delayed): Lock `src_object' earlier, lock `new_copy'.
(vm_object_shadow): Lock `result'.
(vm_object_enter): Properly lock `object'.  Avoid accessing fields
without the lock.
* vm/vm_pageout.c (vm_pageout_setup): Properly lock `old_object'.
---
 vm/vm_map.c | 55 +++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 39 insertions(+), 16 deletions(-)

(limited to 'vm/vm_map.c')

diff --git a/vm/vm_map.c b/vm/vm_map.c
index ae3ce21..9098dfd 100644
--- a/vm/vm_map.c
+++ b/vm/vm_map.c
@@ -1182,16 +1182,20 @@ kern_return_t vm_map_submap(
 
 	if ((entry->vme_start == start) && (entry->vme_end == end) &&
 	    (!entry->is_sub_map) &&
-	    ((object = entry->object.vm_object) == vm_submap_object) &&
-	    (object->resident_page_count == 0) &&
-	    (object->copy == VM_OBJECT_NULL) &&
-	    (object->shadow == VM_OBJECT_NULL) &&
-	    (!object->pager_created)) {
-		entry->object.vm_object = VM_OBJECT_NULL;
-		vm_object_deallocate(object);
-		entry->is_sub_map = TRUE;
-		vm_map_reference(entry->object.sub_map = submap);
-		result = KERN_SUCCESS;
+	    ((object = entry->object.vm_object) == vm_submap_object)) {
+		vm_object_lock(object);
+		if ((object->resident_page_count == 0) &&
+		    (object->copy == VM_OBJECT_NULL) &&
+		    (object->shadow == VM_OBJECT_NULL) &&
+		    (!object->pager_created)) {
+			vm_object_unlock(object);
+			entry->object.vm_object = VM_OBJECT_NULL;
+			vm_object_deallocate(object);
+			entry->is_sub_map = TRUE;
+			vm_map_reference(entry->object.sub_map = submap);
+			result = KERN_SUCCESS;
+		} else
+			vm_object_unlock(object);
 	}
 	vm_map_unlock(map);
 
@@ -2122,6 +2126,7 @@ start_pass_1:
 	for (entry = tmp_entry;;) {
 		vm_size_t	sub_size = (entry->vme_end - entry->vme_start);
 		vm_map_entry_t	next = entry->vme_next;
+		vm_object_t	object;
 
 		if ( ! (entry->protection & VM_PROT_WRITE)) {
 			vm_map_unlock(dst_map);
@@ -2157,10 +2162,13 @@ start_pass_1:
 		/*
 		 *	Check for permanent objects in the destination.
 		 */
-
-		if ((entry->object.vm_object != VM_OBJECT_NULL) &&
-			   !entry->object.vm_object->temporary)
-			contains_permanent_objects = TRUE;
+		object = entry->object.vm_object;
+		if ((object != VM_OBJECT_NULL)
+		    && ! contains_permanent_objects) {
+			vm_object_lock(object);
+			contains_permanent_objects = object->temporary;
+			vm_object_unlock(object);
+		}
 
 		size -= sub_size;
 		entry = next;
@@ -2220,6 +2228,7 @@ start_pass_1:
 		vm_map_entry_t	copy_entry = vm_map_copy_first_entry(copy);
 		vm_size_t	copy_size = (copy_entry->vme_end - copy_entry->vme_start);
 		vm_object_t	object;
+		int		temporary;
 
 		entry = tmp_entry;
 		size = (entry->vme_end - entry->vme_start);
@@ -2275,8 +2284,15 @@ start_pass_1:
 		 */
 
 		object = entry->object.vm_object;
+		temporary = 0;
+		if (object != VM_OBJECT_NULL) {
+			vm_object_lock(object);
+			temporary = object->temporary;
+			vm_object_unlock(object);
+		}
+
 		if (!entry->is_shared &&
-		    ((object == VM_OBJECT_NULL) || object->temporary)) {
+		    ((object == VM_OBJECT_NULL) || temporary)) {
 			vm_object_t	old_object = entry->object.vm_object;
 			vm_offset_t	old_offset = entry->offset;
 
@@ -3219,11 +3235,15 @@ kern_return_t vm_map_copyin(
 		/*
 		 *	Attempt non-blocking copy-on-write optimizations.
 		 */
-
+		if (src_object)
+			vm_object_lock(src_object);
 		if (src_destroy &&
 		    (src_object == VM_OBJECT_NULL ||
 		     (src_object->temporary && !src_object->use_shared_copy)))
 		{
+		    if (src_object)
+			vm_object_unlock(src_object);
+
 		    /*
 		     * If we are destroying the source, and the object
 		     * is temporary, and not shared writable,
@@ -3243,6 +3263,9 @@ kern_return_t vm_map_copyin(
 		    goto CopySuccessful;
 		}
 
+		if (src_object)
+			vm_object_unlock(src_object);
+
 		if (!was_wired &&
 		    vm_object_copy_temporary(
 				&new_entry->object.vm_object,
-- 
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