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Date: Mon, 25 Jan 2016 08:55:51 -0800
From: Laura Abbott <labbott@...oraproject.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Vlastimil Babka <vbabka@...e.cz>, Michal Hocko <mhocko@...e.com>
Cc: Laura Abbott <labbott@...oraproject.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
Kees Cook <keescook@...omium.org>
Subject: [RFC][PATCH 1/3] mm/debug-pagealloc.c: Split out page poisoning from debug page_alloc
For architectures that do not have debug page_alloc
(!ARCH_SUPPORTS_DEBUG_PAGEALLOC), page poisoning is used instead.
Even architectures that do have DEBUG_PAGEALLOC may want to take advantage of
the poisoning feature. Separate out page poisoning into a separate file. This
does not change the default behavior for !ARCH_SUPPORTS_DEBUG_PAGEALLOC.
Credit to Mathias Krause and grsecurity for original work
Signed-off-by: Laura Abbott <labbott@...oraproject.org>
---
Documentation/kernel-parameters.txt | 5 ++
include/linux/mm.h | 10 +++
mm/Makefile | 5 +-
mm/debug-pagealloc.c | 121 +-----------------------------
mm/page_poison.c | 144 ++++++++++++++++++++++++++++++++++++
5 files changed, 164 insertions(+), 121 deletions(-)
create mode 100644 mm/page_poison.c
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index cfb2c0f..343a4f1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2681,6 +2681,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
we can turn it on.
on: enable the feature
+ page_poison= [KNL] Boot-time parameter changing the state of
+ poisoning on the buddy allocator.
+ off: turn off poisoning
+ on: turn on poisoning
+
panic= [KNL] Kernel behaviour on panic: delay <timeout>
timeout > 0: seconds before rebooting
timeout = 0: wait forever
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f1cd22f..25551c1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2174,6 +2174,16 @@ extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
unsigned long size, pte_fn_t fn, void *data);
+#ifdef CONFIG_PAGE_POISONING
+extern void poison_pages(struct page *page, int n);
+extern void unpoison_pages(struct page *page, int n);
+extern bool page_poisoning_enabled(void);
+#else
+static inline void poison_pages(struct page *page, int n) { }
+static inline void unpoison_pages(struct page *page, int n) { }
+static inline bool page_poisoning_enabled(void) { return false; }
+#endif
+
#ifdef CONFIG_DEBUG_PAGEALLOC
extern bool _debug_pagealloc_enabled;
extern void __kernel_map_pages(struct page *page, int numpages, int enable);
diff --git a/mm/Makefile b/mm/Makefile
index 2ed4319..f256978 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -48,7 +48,10 @@ obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o
obj-$(CONFIG_SLOB) += slob.o
obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o
obj-$(CONFIG_KSM) += ksm.o
-obj-$(CONFIG_PAGE_POISONING) += debug-pagealloc.o
+ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
+ obj-$(CONFIG_DEBUG_PAGEALLOC) += debug-pagealloc.o
+endif
+obj-$(CONFIG_PAGE_POISONING) += page_poison.o
obj-$(CONFIG_SLAB) += slab.o
obj-$(CONFIG_SLUB) += slub.o
obj-$(CONFIG_KMEMCHECK) += kmemcheck.o
diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
index 5bf5906..3cc4c1d 100644
--- a/mm/debug-pagealloc.c
+++ b/mm/debug-pagealloc.c
@@ -6,128 +6,9 @@
#include <linux/poison.h>
#include <linux/ratelimit.h>
-static bool page_poisoning_enabled __read_mostly;
-
-static bool need_page_poisoning(void)
-{
- if (!debug_pagealloc_enabled())
- return false;
-
- return true;
-}
-
-static void init_page_poisoning(void)
-{
- if (!debug_pagealloc_enabled())
- return;
-
- page_poisoning_enabled = true;
-}
-
-struct page_ext_operations page_poisoning_ops = {
- .need = need_page_poisoning,
- .init = init_page_poisoning,
-};
-
-static inline void set_page_poison(struct page *page)
-{
- struct page_ext *page_ext;
-
- page_ext = lookup_page_ext(page);
- __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
-}
-
-static inline void clear_page_poison(struct page *page)
-{
- struct page_ext *page_ext;
-
- page_ext = lookup_page_ext(page);
- __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
-}
-
-static inline bool page_poison(struct page *page)
-{
- struct page_ext *page_ext;
-
- page_ext = lookup_page_ext(page);
- return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
-}
-
-static void poison_page(struct page *page)
-{
- void *addr = kmap_atomic(page);
-
- set_page_poison(page);
- memset(addr, PAGE_POISON, PAGE_SIZE);
- kunmap_atomic(addr);
-}
-
-static void poison_pages(struct page *page, int n)
-{
- int i;
-
- for (i = 0; i < n; i++)
- poison_page(page + i);
-}
-
-static bool single_bit_flip(unsigned char a, unsigned char b)
-{
- unsigned char error = a ^ b;
-
- return error && !(error & (error - 1));
-}
-
-static void check_poison_mem(unsigned char *mem, size_t bytes)
-{
- static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
- unsigned char *start;
- unsigned char *end;
-
- start = memchr_inv(mem, PAGE_POISON, bytes);
- if (!start)
- return;
-
- for (end = mem + bytes - 1; end > start; end--) {
- if (*end != PAGE_POISON)
- break;
- }
-
- if (!__ratelimit(&ratelimit))
- return;
- else if (start == end && single_bit_flip(*start, PAGE_POISON))
- printk(KERN_ERR "pagealloc: single bit error\n");
- else
- printk(KERN_ERR "pagealloc: memory corruption\n");
-
- print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
- end - start + 1, 1);
- dump_stack();
-}
-
-static void unpoison_page(struct page *page)
-{
- void *addr;
-
- if (!page_poison(page))
- return;
-
- addr = kmap_atomic(page);
- check_poison_mem(addr, PAGE_SIZE);
- clear_page_poison(page);
- kunmap_atomic(addr);
-}
-
-static void unpoison_pages(struct page *page, int n)
-{
- int i;
-
- for (i = 0; i < n; i++)
- unpoison_page(page + i);
-}
-
void __kernel_map_pages(struct page *page, int numpages, int enable)
{
- if (!page_poisoning_enabled)
+ if (!page_poisoning_enabled())
return;
if (enable)
diff --git a/mm/page_poison.c b/mm/page_poison.c
new file mode 100644
index 0000000..0f369a6
--- /dev/null
+++ b/mm/page_poison.c
@@ -0,0 +1,144 @@
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
+#include <linux/page_ext.h>
+#include <linux/poison.h>
+#include <linux/ratelimit.h>
+
+static bool __page_poisoning_enabled __read_mostly;
+static bool want_page_poisoning __read_mostly =
+ !IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC);
+
+static int early_page_poison_param(char *buf)
+{
+ if (!buf)
+ return -EINVAL;
+
+ if (strcmp(buf, "on") == 0)
+ want_page_poisoning = true;
+ else if (strcmp(buf, "off") == 0)
+ want_page_poisoning = false;
+
+ return 0;
+}
+early_param("page_poison", early_page_poison_param);
+
+bool page_poisoning_enabled(void)
+{
+ return __page_poisoning_enabled;
+}
+
+static bool need_page_poisoning(void)
+{
+ return want_page_poisoning;
+}
+
+static void init_page_poisoning(void)
+{
+ if (!want_page_poisoning)
+ return;
+
+ __page_poisoning_enabled = true;
+}
+
+struct page_ext_operations page_poisoning_ops = {
+ .need = need_page_poisoning,
+ .init = init_page_poisoning,
+};
+
+static inline void set_page_poison(struct page *page)
+{
+ struct page_ext *page_ext;
+
+ page_ext = lookup_page_ext(page);
+ __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
+}
+
+static inline void clear_page_poison(struct page *page)
+{
+ struct page_ext *page_ext;
+
+ page_ext = lookup_page_ext(page);
+ __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
+}
+
+static inline bool page_poison(struct page *page)
+{
+ struct page_ext *page_ext;
+
+ page_ext = lookup_page_ext(page);
+ return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
+}
+
+static void poison_page(struct page *page)
+{
+ void *addr = kmap_atomic(page);
+
+ set_page_poison(page);
+ memset(addr, PAGE_POISON, PAGE_SIZE);
+ kunmap_atomic(addr);
+}
+
+void poison_pages(struct page *page, int n)
+{
+ int i;
+
+ for (i = 0; i < n; i++)
+ poison_page(page + i);
+}
+
+static bool single_bit_flip(unsigned char a, unsigned char b)
+{
+ unsigned char error = a ^ b;
+
+ return error && !(error & (error - 1));
+}
+
+static void check_poison_mem(unsigned char *mem, size_t bytes)
+{
+ static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
+ unsigned char *start;
+ unsigned char *end;
+
+ start = memchr_inv(mem, PAGE_POISON, bytes);
+ if (!start)
+ return;
+
+ for (end = mem + bytes - 1; end > start; end--) {
+ if (*end != PAGE_POISON)
+ break;
+ }
+
+ if (!__ratelimit(&ratelimit))
+ return;
+ else if (start == end && single_bit_flip(*start, PAGE_POISON))
+ printk(KERN_ERR "pagealloc: single bit error\n");
+ else
+ printk(KERN_ERR "pagealloc: memory corruption\n");
+
+ print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
+ end - start + 1, 1);
+ dump_stack();
+}
+
+static void unpoison_page(struct page *page)
+{
+ void *addr;
+
+ if (!page_poison(page))
+ return;
+
+ addr = kmap_atomic(page);
+ check_poison_mem(addr, PAGE_SIZE);
+ clear_page_poison(page);
+ kunmap_atomic(addr);
+}
+
+void unpoison_pages(struct page *page, int n)
+{
+ int i;
+
+ for (i = 0; i < n; i++)
+ unpoison_page(page + i);
+}
--
2.5.0
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