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-rw-r--r--mm/Kconfig.debug25
-rw-r--r--mm/Makefile2
-rw-r--r--mm/page_alloc.c2
-rw-r--r--mm/page_poison.c (renamed from mm/debug-pagealloc.c)60
4 files changed, 75 insertions, 14 deletions
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index a0c136af9c91..1f99f9a0deae 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -41,4 +41,27 @@ config DEBUG_PAGEALLOC_ENABLE_DEFAULT
can be overridden by debug_pagealloc=off|on.
config PAGE_POISONING
- bool
+ bool "Poison pages after freeing"
+ select PAGE_EXTENSION
+ select PAGE_POISONING_NO_SANITY if HIBERNATION
+ ---help---
+ Fill the pages with poison patterns after free_pages() and verify
+ the patterns before alloc_pages. The filling of the memory helps
+ reduce the risk of information leaks from freed data. This does
+ have a potential performance impact.
+
+ Note that "poison" here is not the same thing as the "HWPoison"
+ for CONFIG_MEMORY_FAILURE. This is software poisoning only.
+
+ If unsure, say N
+
+config PAGE_POISONING_NO_SANITY
+ depends on PAGE_POISONING
+ bool "Only poison, don't sanity check"
+ ---help---
+ Skip the sanity checking on alloc, only fill the pages with
+ poison on free. This reduces some of the overhead of the
+ poisoning feature.
+
+ If you are only interested in sanitization, say Y. Otherwise
+ say N.
diff --git a/mm/Makefile b/mm/Makefile
index 2ed43191fc3b..cfdd481d27a5 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -48,7 +48,7 @@ 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-$(CONFIG_PAGE_POISONING) += debug-pagealloc.o
+obj-$(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/page_alloc.c b/mm/page_alloc.c
index 0691403aed93..2a08349fbab2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1025,6 +1025,7 @@ static bool free_pages_prepare(struct page *page, unsigned int order)
PAGE_SIZE << order);
}
arch_free_page(page, order);
+ kernel_poison_pages(page, 1 << order, 0);
kernel_map_pages(page, 1 << order, 0);
return true;
@@ -1420,6 +1421,7 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
arch_alloc_page(page, order);
kernel_map_pages(page, 1 << order, 1);
+ kernel_poison_pages(page, 1 << order, 1);
kasan_alloc_pages(page, order);
if (gfp_flags & __GFP_ZERO)
diff --git a/mm/debug-pagealloc.c b/mm/page_poison.c
index 5bf5906ce13b..89d3bc773633 100644
--- a/mm/debug-pagealloc.c
+++ b/mm/page_poison.c
@@ -6,22 +6,48 @@
#include <linux/poison.h>
#include <linux/ratelimit.h>
-static bool page_poisoning_enabled __read_mostly;
+static bool __page_poisoning_enabled __read_mostly;
+static bool want_page_poisoning __read_mostly;
-static bool need_page_poisoning(void)
+static int early_page_poison_param(char *buf)
{
- if (!debug_pagealloc_enabled())
- return false;
+ if (!buf)
+ return -EINVAL;
+
+ if (strcmp(buf, "on") == 0)
+ want_page_poisoning = true;
+ else if (strcmp(buf, "off") == 0)
+ want_page_poisoning = false;
- return true;
+ 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 (!debug_pagealloc_enabled())
- return;
+ /*
+ * page poisoning is debug page alloc for some arches. If either
+ * of those options are enabled, enable poisoning
+ */
+ if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC)) {
+ if (!want_page_poisoning && !debug_pagealloc_enabled())
+ return;
+ } else {
+ if (!want_page_poisoning)
+ return;
+ }
- page_poisoning_enabled = true;
+ __page_poisoning_enabled = true;
}
struct page_ext_operations page_poisoning_ops = {
@@ -83,6 +109,9 @@ static void check_poison_mem(unsigned char *mem, size_t bytes)
unsigned char *start;
unsigned char *end;
+ if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
+ return;
+
start = memchr_inv(mem, PAGE_POISON, bytes);
if (!start)
return;
@@ -95,9 +124,9 @@ static void check_poison_mem(unsigned char *mem, size_t bytes)
if (!__ratelimit(&ratelimit))
return;
else if (start == end && single_bit_flip(*start, PAGE_POISON))
- printk(KERN_ERR "pagealloc: single bit error\n");
+ pr_err("pagealloc: single bit error\n");
else
- printk(KERN_ERR "pagealloc: memory corruption\n");
+ pr_err("pagealloc: memory corruption\n");
print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
end - start + 1, 1);
@@ -125,9 +154,9 @@ static void unpoison_pages(struct page *page, int n)
unpoison_page(page + i);
}
-void __kernel_map_pages(struct page *page, int numpages, int enable)
+void kernel_poison_pages(struct page *page, int numpages, int enable)
{
- if (!page_poisoning_enabled)
+ if (!page_poisoning_enabled())
return;
if (enable)
@@ -135,3 +164,10 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
else
poison_pages(page, numpages);
}
+
+#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
+void __kernel_map_pages(struct page *page, int numpages, int enable)
+{
+ /* This function does nothing, all work is done via poison pages */
+}
+#endif