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Message-Id: <20190418154208.131118-3-glider@google.com>
Date: Thu, 18 Apr 2019 17:42:07 +0200
From: Alexander Potapenko <glider@...gle.com>
To: akpm@...ux-foundation.org, cl@...ux.com, dvyukov@...gle.com,
keescook@...omium.org, labbott@...hat.com
Cc: linux-mm@...ck.org, linux-security-module@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH 2/3] gfp: mm: introduce __GFP_NOINIT
When passed to an allocator (either pagealloc or SL[AOU]B), __GFP_NOINIT
tells it to not initialize the requested memory if the init_allocations
boot option is enabled. This can be useful in the cases the newly
allocated memory is going to be initialized by the caller right away.
__GFP_NOINIT basically defeats the hardening against information leaks
provided by the init_allocations feature, so one should use it with
caution.
This patch also adds __GFP_NOINIT to alloc_pages() calls in SL[AOU]B.
Signed-off-by: Alexander Potapenko <glider@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: James Morris <jmorris@...ei.org>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Kostya Serebryany <kcc@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Sandeep Patil <sspatil@...roid.com>
Cc: Laura Abbott <labbott@...hat.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Jann Horn <jannh@...gle.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Qian Cai <cai@....pw>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: linux-mm@...ck.org
Cc: linux-security-module@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com
---
include/linux/gfp.h | 6 +++++-
include/linux/mm.h | 2 +-
kernel/kexec_core.c | 2 +-
mm/slab.c | 2 +-
mm/slob.c | 1 +
mm/slub.c | 1 +
6 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index fdab7de7490d..66d7f5604fe2 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -44,6 +44,7 @@ struct vm_area_struct;
#else
#define ___GFP_NOLOCKDEP 0
#endif
+#define ___GFP_NOINIT 0x1000000u
/* If the above are modified, __GFP_BITS_SHIFT may need updating */
/*
@@ -208,16 +209,19 @@ struct vm_area_struct;
* %__GFP_COMP address compound page metadata.
*
* %__GFP_ZERO returns a zeroed page on success.
+ *
+ * %__GFP_NOINIT requests non-initialized memory from the underlying allocator.
*/
#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN)
#define __GFP_COMP ((__force gfp_t)___GFP_COMP)
#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO)
+#define __GFP_NOINIT ((__force gfp_t)___GFP_NOINIT)
/* Disable lockdep for GFP context tracking */
#define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
/* Room for N __GFP_FOO bits */
-#define __GFP_BITS_SHIFT (23 + IS_ENABLED(CONFIG_LOCKDEP))
+#define __GFP_BITS_SHIFT (25)
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
/**
diff --git a/include/linux/mm.h b/include/linux/mm.h
index b38b71a5efaa..8f03334a9033 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2601,7 +2601,7 @@ DECLARE_STATIC_KEY_FALSE(init_allocations);
static inline bool want_init_memory(gfp_t flags)
{
if (static_branch_unlikely(&init_allocations))
- return true;
+ return !(flags & __GFP_NOINIT);
return flags & __GFP_ZERO;
}
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index be84f5f95c97..f9d1f1236cd0 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -302,7 +302,7 @@ static struct page *kimage_alloc_pages(gfp_t gfp_mask, unsigned int order)
{
struct page *pages;
- pages = alloc_pages(gfp_mask & ~__GFP_ZERO, order);
+ pages = alloc_pages((gfp_mask & ~__GFP_ZERO) | __GFP_NOINIT, order);
if (pages) {
unsigned int count, i;
diff --git a/mm/slab.c b/mm/slab.c
index dcc5b73cf767..762cb0e7bcc1 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1393,7 +1393,7 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
struct page *page;
int nr_pages;
- flags |= cachep->allocflags;
+ flags |= (cachep->allocflags | __GFP_NOINIT);
page = __alloc_pages_node(nodeid, flags, cachep->gfporder);
if (!page) {
diff --git a/mm/slob.c b/mm/slob.c
index 18981a71e962..867d2d68a693 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -192,6 +192,7 @@ static void *slob_new_pages(gfp_t gfp, int order, int node)
{
void *page;
+ gfp |= __GFP_NOINIT;
#ifdef CONFIG_NUMA
if (node != NUMA_NO_NODE)
page = __alloc_pages_node(node, gfp, order);
diff --git a/mm/slub.c b/mm/slub.c
index e4efb6575510..a79b4cb768a2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1493,6 +1493,7 @@ static inline struct page *alloc_slab_page(struct kmem_cache *s,
struct page *page;
unsigned int order = oo_order(oo);
+ flags |= __GFP_NOINIT;
if (node == NUMA_NO_NODE)
page = alloc_pages(flags, order);
else
--
2.21.0.392.gf8f6787159e-goog
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