Patch "kaiser: stack map PAGE_SIZE at THREAD_SIZE-PAGE_SIZE" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

kaiser: stack map PAGE_SIZE at THREAD_SIZE-PAGE_SIZE

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kaiser-stack-map-page_size-at-thread_size-page_size.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Hugh Dickins <[email protected]>
Date: Sun, 3 Sep 2017 18:57:03 -0700
Subject: kaiser: stack map PAGE_SIZE at THREAD_SIZE-PAGE_SIZE

From: Hugh Dickins <[email protected]>

Kaiser only needs to map one page of the stack; and kernel/fork.c did not build on powerpc (no __PAGE_KERNEL). It's all cleaner if linux/kaiser.h provides kaiser_map_thread_stack() and kaiser_unmap_thread_stack() wrappers around asm/kaiser.h's kaiser_add_mapping() and kaiser_remove_mapping(). And use linux/kaiser.h in init/main.c to avoid the #ifdefs there.

---
 include/linux/kaiser.h |   40 +++++++++++++++++++++++++++++++++-------
 init/main.c            |    6 +-----
 kernel/fork.c          |    7 ++-----
 3 files changed, 36 insertions(+), 17 deletions(-)

@@ -1,26 +1,52 @@
-#ifndef _INCLUDE_KAISER_H
-#define _INCLUDE_KAISER_H
+#ifndef _LINUX_KAISER_H
+#define _LINUX_KAISER_H
 
 #ifdef CONFIG_KAISER
 #include <asm/kaiser.h>
+
+static inline int kaiser_map_thread_stack(void *stack)
+{
+	/*
+	 * Map that page of kernel stack on which we enter from user context.
+	 */
+	return kaiser_add_mapping((unsigned long)stack +
+			THREAD_SIZE - PAGE_SIZE, PAGE_SIZE, __PAGE_KERNEL);
+}
+
+static inline void kaiser_unmap_thread_stack(void *stack)
+{
+	/*
+	 * Note: may be called even when kaiser_map_thread_stack() failed.
+	 */
+	kaiser_remove_mapping((unsigned long)stack +
+			THREAD_SIZE - PAGE_SIZE, PAGE_SIZE);
+}
 #else
 
 /*
  * These stubs are used whenever CONFIG_KAISER is off, which
- * includes architectures that support KAISER, but have it
- * disabled.
+ * includes architectures that support KAISER, but have it disabled.
  */
 
 static inline void kaiser_init(void)
 {
 }
-static inline void kaiser_remove_mapping(unsigned long start, unsigned long size)
+static inline int kaiser_add_mapping(unsigned long addr,
+				     unsigned long size, unsigned long flags)
+{
+	return 0;
+}
+static inline void kaiser_remove_mapping(unsigned long start,
+					 unsigned long size)
 {
 }
-static inline int kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags)
+static inline int kaiser_map_thread_stack(void *stack)
 {
 	return 0;
 }
+static inline void kaiser_unmap_thread_stack(void *stack)
+{
+}
 
 #endif /* !CONFIG_KAISER */
-#endif /* _INCLUDE_KAISER_H */
+#endif /* _LINUX_KAISER_H */

@@ -80,15 +80,13 @@
 #include <linux/integrity.h>
 #include <linux/proc_ns.h>
 #include <linux/io.h>
+#include <linux/kaiser.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
 #include <asm/setup.h>
 #include <asm/sections.h>
 #include <asm/cacheflush.h>
-#ifdef CONFIG_KAISER
-#include <asm/kaiser.h>
-#endif
 
 static int kernel_init(void *);
 

@@ -476,9 +474,7 @@ static void __init mm_init(void)
 	pgtable_init();
 	vmalloc_init();
 	ioremap_huge_init();
-#ifdef CONFIG_KAISER
 	kaiser_init();
-#endif
 }
 
 asmlinkage __visible void __init start_kernel(void)

@@ -212,12 +212,9 @@ static unsigned long *alloc_thread_stack
 #endif
 }
 
-extern void kaiser_remove_mapping(unsigned long start_addr, unsigned long size);
 static inline void free_thread_stack(struct task_struct *tsk)
 {
-#ifdef CONFIG_KAISER
-	kaiser_remove_mapping((unsigned long)tsk->stack, THREAD_SIZE);
-#endif
+	kaiser_unmap_thread_stack(tsk->stack);
 #ifdef CONFIG_VMAP_STACK
 	if (task_stack_vm_area(tsk)) {
 		unsigned long flags;

@@ -501,7 +498,7 @@ static struct task_struct *dup_task_stru
 	 */
 	tsk->stack = stack;
 
-	err= kaiser_add_mapping((unsigned long)tsk->stack, THREAD_SIZE, __PAGE_KERNEL);
+	err= kaiser_map_thread_stack(tsk->stack);
 	if (err)
 		goto free_stack;
 #ifdef CONFIG_VMAP_STACK

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kaiser-vmstat-show-nr_kaisertable-as-nr_overhead.patch queue-4.9/kaiser-add-nokaiser-boot-option-using-alternative.patch queue-4.9/kaiser-fix-unlikely-error-in-alloc_ldt_struct.patch queue-4.9/kaiser-kaiser_flush_tlb_on_return_to_user-check-pcid.patch queue-4.9/x86-paravirt-dont-patch-flush_tlb_single.patch queue-4.9/kaiser-merged-update.patch queue-4.9/kaiser-delete-kaiser_real_switch-option.patch queue-4.9/kaiser-kaiser_remove_mapping-move-along-the-pgd.patch queue-4.9/kaiser-fix-perf-crashes.patch queue-4.9/kaiser-drop-is_atomic-arg-to-kaiser_pagetable_walk.patch queue-4.9/kaiser-load_new_mm_cr3-let-switch_user_cr3-flush-user.patch queue-4.9/kaiser-enhanced-by-kernel-and-user-pcids.patch queue-4.9/kaiser-x86_cr3_pcid_noflush-and-x86_cr3_pcid_user.patch queue-4.9/kaiser-align-addition-to-x86-mm-makefile.patch queue-4.9/kaiser-use-alternative-instead-of-x86_cr3_pcid_noflush.patch queue-4.9/kaiser-stack-map-page_size-at-thread_size-page_size.patch queue-4.9/kaiser-name-that-0x1000-kaiser_shadow_pgd_offset.patch queue-4.9/kaiser-fix-regs-to-do_nmi-ifndef-config_kaiser.patch queue-4.9/kaiser-do-not-set-_page_nx-on-pgd_none.patch queue-4.9/kaiser-tidied-up-asm-kaiser.h-somewhat.patch queue-4.9/kaiser-cleanups-while-trying-for-gold-link.patch queue-4.9/kaiser-tidied-up-kaiser_add-remove_mapping-slightly.patch queue-4.9/kaiser-fix-build-and-fixme-in-alloc_ldt_struct.patch queue-4.9/kaiser-kernel-address-isolation.patch queue-4.9/kaiser-enomem-if-kaiser_pagetable_walk-null.patch queue-4.9/kaiser-asm-tlbflush.h-handle-nopge-at-lower-level.patch queue-4.9/kaiser-paranoid_entry-pass-cr3-need-to-paranoid_exit.patch queue-4.9/kaiser-kaiser-depends-on-smp.patch queue-4.9/kaiser-pcid-0-for-kernel-and-128-for-user.patch