diff --git a/fs/buffer.c b/fs/buffer.c
index 28484b3..b524eda 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3511,7 +3511,7 @@ void __init buffer_init(void)
  bh_cachep = kmem_cache_create("buffer_head",
  sizeof(struct buffer_head), 0,
  (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
- SLAB_MEM_SPREAD),
+ SLAB_MEM_SPREAD|SLAB_NO_SANITIZE),
  NULL);

  /*
diff --git a/fs/dcache.c b/fs/dcache.c
index 95d71ed..77abd2f 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3616,8 +3616,16 @@ void __init vfs_caches_init_early(void)

 void __init vfs_caches_init(void)
 {
+/**
+ names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC| SLAB_NO_SANITIZE,
+ 0, PATH_MAX, NULL);
+ kmem_cache_create_usercopy() unavailable for now at least.
+ So just adding the SLAB_NO_SANITIZE flag to the usual call below..
+ */
  names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NO_SANITIZE, NULL);
+

  dcache_init();
  inode_init();
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index bb3f329..9daed55 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -190,6 +190,18 @@ static inline void clear_highpage(struct page *page)
  kunmap_atomic(kaddr);
 }

+static inline void sanitize_highpage(struct page *page)
+{
+ void *kaddr;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ kaddr = kmap_atomic(page);
+ clear_page(kaddr);
+ kunmap_atomic(kaddr);
+ local_irq_restore(flags);
+}
+
 static inline void zero_user_segments(struct page *page,
  unsigned start1, unsigned end1,
  unsigned start2, unsigned end2)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 4c53635..334bd89 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -23,6 +23,13 @@
 #define SLAB_CONSISTENCY_CHECKS 0x00000100UL /* DEBUG: Perform
(expensive) checks on alloc/free */
 #define SLAB_RED_ZONE 0x00000400UL /* DEBUG: Red zone objs in a cache */
 #define SLAB_POISON 0x00000800UL /* DEBUG: Poison objects */
+
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+#define SLAB_NO_SANITIZE 0x00001000UL /* PaX: Do not sanitize objs on free */
+#else
+#define SLAB_NO_SANITIZE 0x00000000UL
+#endif
+
 #define SLAB_HWCACHE_ALIGN 0x00002000UL /* Align objs on cache lines */
 #define SLAB_CACHE_DMA 0x00004000UL /* Use GFP_DMA memory */
 #define SLAB_STORE_USER 0x00010000UL /* DEBUG: Store the last owner
for bug hunting */
diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index 4ad2c5a..a30bbd2 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -60,6 +60,10 @@ struct kmem_cache {
  atomic_t allocmiss;
  atomic_t freehit;
  atomic_t freemiss;
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ atomic_unchecked_t sanitized;
+ atomic_unchecked_t not_sanitized;
+#endif
 #ifdef CONFIG_DEBUG_SLAB_LEAK
  atomic_t store_user_clean;
 #endif
diff --git a/kernel/fork.c b/kernel/fork.c
index 7da33cb..24404a6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2098,7 +2098,7 @@ void __init proc_caches_init(void)
  sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
  SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
  NULL);
- vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
+ vm_area_cachep = KMEM_CACHE(vm_area_struct,
SLAB_PANIC|SLAB_ACCOUNT|SLAB_NO_SANITIZE);
  mmap_init();
  nsproxy_cache_init();
 }
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index afcc550..ed3f097 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -10,6 +10,7 @@ config PAGE_EXTENSION
 config DEBUG_PAGEALLOC
  bool "Debug page memory allocations"
  depends on DEBUG_KERNEL
+ depends on !PAX_MEMORY_SANITIZE
  depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
  depends on !KMEMCHECK
  select PAGE_EXTENSION
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 21ea508..d7b3d95 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -994,6 +994,10 @@ static __always_inline bool
free_pages_prepare(struct page *page,
 {
  int bad = 0;

+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ unsigned long index = 1UL << order;
+#endif
+
  VM_BUG_ON_PAGE(PageTail(page), page);

  trace_mm_page_free(page, order);
@@ -1040,6 +1044,12 @@ static __always_inline bool
free_pages_prepare(struct page *page,
  debug_check_no_obj_freed(page_address(page),
    PAGE_SIZE << order);
  }
+
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ for (; index; --index)
+ sanitize_highpage(page + index - 1);
+#endif
+
  arch_free_page(page, order);
  kernel_poison_pages(page, 1 << order, 0);
  kernel_map_pages(page, 1 << order, 0);
@@ -1696,8 +1706,9 @@ static inline int check_new_page(struct page *page)

 static inline bool free_pages_prezeroed(bool poisoned)
 {
- return IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) &&
- page_poisoning_enabled() && poisoned;
+ return IS_ENABLED(CONFIG_PAX_MEMORY_SANITIZE) ||
+ (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) && page_poisoning_enabled()
&& poisoned);
+
 }

 #ifdef CONFIG_DEBUG_VM
@@ -1753,11 +1764,13 @@ static void prep_new_page(struct page *page,
unsigned int order, gfp_t gfp_flags
  int i;
  bool poisoned = true;

+#ifndef CONFIG_PAX_MEMORY_SANITIZE
  for (i = 0; i < (1 << order); i++) {
  struct page *p = page + i;
  if (poisoned)
  poisoned &= page_is_poisoned(p);
  }
+#endif

  post_alloc_hook(page, order, gfp_flags);

diff --git a/mm/rmap.c b/mm/rmap.c
index 91619fd..c97da9e 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -428,10 +428,10 @@ static void anon_vma_ctor(void *data)
 void __init anon_vma_init(void)
 {
  anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
- 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
+ 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT|SLAB_NO_SANITIZE,
  anon_vma_ctor);
  anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
- SLAB_PANIC|SLAB_ACCOUNT);
+ SLAB_PANIC|SLAB_ACCOUNT|SLAB_NO_SANITIZE);
 }

 /*
diff --git a/mm/slab.c b/mm/slab.c
index 4f2ec6b..6dc9f4a 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3511,6 +3511,20 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
  struct array_cache *ac = cpu_cache_get(cachep);

  check_irq_off();
+
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ if (cachep->flags & (SLAB_POISON | SLAB_NO_SANITIZE))
+ STATS_INC_NOT_SANITIZED(cachep);
+ else {
+ memset(objp, PAX_MEMORY_SANITIZE_VALUE, cachep->object_size);
+
+ if (cachep->ctor)
+ cachep->ctor(objp);
+
+ STATS_INC_SANITIZED(cachep);
+ }
+#endif
+
  kmemleak_free_recursive(objp, cachep->flags);
  objp = cache_free_debugcheck(cachep, objp, caller);

@@ -4157,6 +4171,14 @@ void slabinfo_show_stats(struct seq_file *m,
struct kmem_cache *cachep)
  seq_printf(m, " : cpustat %6lu %6lu %6lu %6lu",
    allochit, allocmiss, freehit, freemiss);
  }
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ {
+ unsigned long sanitized = atomic_read_unchecked(&cachep->sanitized);
+ unsigned long not_sanitized = atomic_read_unchecked(&cachep->not_sanitized);
+
+ seq_printf(m, " : pax %6lu %6lu", sanitized, not_sanitized);
+ }
+#endif
 #endif
 }

diff --git a/mm/slab.h b/mm/slab.h
index de6579d..e982e3b 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -71,6 +71,35 @@ extern struct list_head slab_caches;
 /* The slab cache that manages slab cache information */
 extern struct kmem_cache *kmem_cache;

+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+#ifdef CONFIG_X86_64
+#define PAX_MEMORY_SANITIZE_VALUE '\xfe'
+#else
+#define PAX_MEMORY_SANITIZE_VALUE '\xff'
+#endif
+enum pax_sanitize_mode {
+ PAX_SANITIZE_SLAB_OFF = 0,
+ PAX_SANITIZE_SLAB_FAST,
+ PAX_SANITIZE_SLAB_FULL,
+};
+
+extern enum pax_sanitize_mode pax_sanitize_slab;
+
+static inline unsigned long pax_sanitize_slab_flags(unsigned long flags)
+{
+ if (pax_sanitize_slab == PAX_SANITIZE_SLAB_OFF || (flags &
SLAB_DESTROY_BY_RCU))
+ flags |= SLAB_NO_SANITIZE;
+ else if (pax_sanitize_slab == PAX_SANITIZE_SLAB_FULL)
+ flags &= ~SLAB_NO_SANITIZE;
+ return flags;
+}
+#else
+static inline unsigned long pax_sanitize_slab_flags(unsigned long flags)
+{
+ return flags;
+}
+#endif
+
 unsigned long calculate_alignment(unsigned long flags,
  unsigned long align, unsigned long size);

@@ -120,7 +149,7 @@ static inline unsigned long
kmem_cache_flags(unsigned long object_size,

 /* Legal flag mask for kmem_cache_create(), for various configurations */
 #define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | SLAB_PANIC | \
- SLAB_DESTROY_BY_RCU | SLAB_DEBUG_OBJECTS )
+ SLAB_DESTROY_BY_RCU | SLAB_DEBUG_OBJECTS | SLAB_NO_SANITIZE)

 #if defined(CONFIG_DEBUG_SLAB)
 #define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 1dfc209..80bf59e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -30,6 +30,37 @@ LIST_HEAD(slab_caches);
 DEFINE_MUTEX(slab_mutex);
 struct kmem_cache *kmem_cache;

+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+/**
+enum pax_sanitize_mode pax_sanitize_slab __read_only = PAX_SANITIZE_SLAB_FAST;
+
+?? -above orig statement from the grsec-4.8.17 patch fails compile with:
+mm/slab_common.c:34:37: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
‘__attribute__’ before ‘__read_only’
+ pax_sanitize_mode pax_sanitize_slab __read_only = PAX_SANITIZE_SLAB_FAST;
+*/
+enum pax_sanitize_mode pax_sanitize_slab = PAX_SANITIZE_SLAB_FAST;
+static int __init pax_sanitize_slab_setup(char *str)
+{
+ if (!str)
+ return 0;
+
+ if (!strcmp(str, "0") || !strcmp(str, "off")) {
+ pr_info("PaX slab sanitization: %s\n", "disabled");
+ pax_sanitize_slab = PAX_SANITIZE_SLAB_OFF;
+ } else if (!strcmp(str, "1") || !strcmp(str, "fast")) {
+ pr_info("PaX slab sanitization: %s\n", "fast");
+ pax_sanitize_slab = PAX_SANITIZE_SLAB_FAST;
+ } else if (!strcmp(str, "full")) {
+ pr_info("PaX slab sanitization: %s\n", "full");
+ pax_sanitize_slab = PAX_SANITIZE_SLAB_FULL;
+ } else
+ pr_err("PaX slab sanitization: unsupported option '%s'\n", str);
+
+ return 0;
+}
+early_param("pax_sanitize_slab", pax_sanitize_slab_setup);
+#endif
+
 /*
  * Set of flags that will prevent slab merging
  */
@@ -1136,6 +1167,9 @@ static void print_slabinfo_header(struct seq_file *m)
 #ifdef CONFIG_DEBUG_SLAB
  seq_puts(m, " : globalstat <listallocs> <maxobjs> <grown> <reaped>
<error> <maxfreeable> <nodeallocs> <remotefrees> <alienoverflow>");
  seq_puts(m, " : cpustat <allochit> <allocmiss> <freehit> <freemiss>");
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ seq_puts(m, " : pax <sanitized> <not_sanitized>");
+#endif
 #endif
  seq_putc(m, '\n');
 }
diff --git a/mm/slob.c b/mm/slob.c
index eac04d43..f455845 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -365,6 +365,11 @@ static void slob_free(void *block, int size)
  return;
  }

+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ if (pax_sanitize_slab && !(c && (c->flags & SLAB_NO_SANITIZE)))
+ memset(block, PAX_MEMORY_SANITIZE_VALUE, size);
+#endif
+
  if (!slob_page_free(sp)) {
  /* This slob page is about to become partially free. Easy! */
  sp->units = units;
diff --git a/mm/slub.c b/mm/slub.c
index 067598a..9253eb6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2911,6 +2911,23 @@ static __always_inline void do_slab_free(struct
kmem_cache *s,
  void *tail_obj = tail ? : head;
  struct kmem_cache_cpu *c;
  unsigned long tid;
+
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ if (!(s->flags & SLAB_NO_SANITIZE)) {
+ int offset = s->offset ? 0 : sizeof(void *);
+ void *x = head;
+
+ while (1) {
+ memset(x + offset, PAX_MEMORY_SANITIZE_VALUE, s->object_size - offset);
+ if (s->ctor)
+ s->ctor(x);
+ if (x == tail_obj)
+ break;
+ x = get_freepointer(s, x);
+ }
+ }
+#endif
+
 redo:
  /*
  * Determine the currently cpus per cpu slab.
@@ -5316,6 +5333,15 @@ static struct attribute *slab_attrs[] = {
 #ifdef CONFIG_ZONE_DMA
  &cache_dma_attr.attr,
 #endif
+/**
+#ifdef CONFIG_PAX_MEMORY_SANITIZE
+ &sanitize_attr.attr,
+ * ?? -above statement from the grsec-4.8.17 patch fails compile with:
+ mm/slub.c:5337:3: error: ‘sanitize_attr’ undeclared here (not in a function)
+  &sanitize_attr.attr,
+  ...
+#endif
+ */
 #ifdef CONFIG_NUMA
  &remote_node_defrag_ratio_attr.attr,
 #endif
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7ad67d7..dde2364 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3453,12 +3453,14 @@ void __init skb_init(void)
  skbuff_head_cache = kmem_cache_create("skbuff_head_cache",
       sizeof(struct sk_buff),
       0,
-      SLAB_HWCACHE_ALIGN|SLAB_PANIC,
+      SLAB_HWCACHE_ALIGN|SLAB_PANIC|
+      SLAB_NO_SANITIZE,
       NULL);
  skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
  sizeof(struct sk_buff_fclones),
  0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC,
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC|
+ SLAB_NO_SANITIZE,
  NULL);
 }

diff --git a/security/Kconfig b/security/Kconfig
index 118f454..3ad5110 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -4,6 +4,46 @@

 menu "Security options"

+menu "Miscellaneous hardening features"
+
+config PAX_MEMORY_SANITIZE
+ bool "Sanitize all freed memory"
+ default y if (GRKERNSEC_CONFIG_AUTO && GRKERNSEC_CONFIG_PRIORITY_SECURITY)
+ help
+  By saying Y here the kernel will erase memory pages and slab objects
+  as soon as they are freed.  This in turn reduces the lifetime of data
+  stored in them, making it less likely that sensitive information such
+  as passwords, cryptographic secrets, etc stay in memory for too long.
+
+  This is especially useful for programs whose runtime is short, long
+  lived processes and the kernel itself benefit from this as long as
+  they ensure timely freeing of memory that may hold sensitive
+  information.
+
+  A nice side effect of the sanitization of slab objects is the
+  reduction of possible info leaks caused by padding bytes within the
+  leaky structures.  Use-after-free bugs for structures containing
+  pointers can also be detected as dereferencing the sanitized pointer
+  will generate an access violation.
+
+  The tradeoff is performance impact, on a single CPU system kernel
+  compilation sees a 3% slowdown, other systems and workloads may vary
+  and you are advised to test this feature on your expected workload
+  before deploying it.
+
+  The slab sanitization feature excludes a few slab caches per default
+  for performance reasons.  To extend the feature to cover those as
+  well, pass "pax_sanitize_slab=full" as kernel command line parameter.
+
+  To reduce the performance penalty by sanitizing pages only, albeit
+  limiting the effectiveness of this feature at the same time, slab
+  sanitization can be disabled with the kernel command line parameter
+  "pax_sanitize_slab=off".
+
+  Note that this feature does not protect data stored in live pages,
+  e.g., process memory swapped to disk may stay there for a long time.
+endmenu
+
 source security/keys/Kconfig

 config SECURITY_DMESG_RESTRICT
