1 files changed, 144 insertions, 0 deletions
diff --git a/mm/page_poison.c b/mm/page_poison.c
new file mode 100644
index 000000000..ae0482cde
--- /dev/null
+++ b/mm/page_poison.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+#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>
+#include <linux/kasan.h>
+
+static DEFINE_STATIC_KEY_FALSE_RO(want_page_poisoning);
+
+static int __init early_page_poison_param(char *buf)
+{
+	int ret;
+	bool tmp;
+
+	ret = strtobool(buf, &tmp);
+	if (ret)
+		return ret;
+
+	if (tmp)
+		static_branch_enable(&want_page_poisoning);
+	else
+		static_branch_disable(&want_page_poisoning);
+
+	return 0;
+}
+early_param("page_poison", early_page_poison_param);
+
+/**
+ * page_poisoning_enabled - check if page poisoning is enabled
+ *
+ * Return true if page poisoning is enabled, or false if not.
+ */
+bool page_poisoning_enabled(void)
+{
+	/*
+	 * Assumes that debug_pagealloc_enabled is set before
+	 * memblock_free_all.
+	 * Page poisoning is debug page alloc for some arches. If
+	 * either of those options are enabled, enable poisoning.
+	 */
+	return (static_branch_unlikely(&want_page_poisoning) ||
+		(!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
+		debug_pagealloc_enabled()));
+}
+EXPORT_SYMBOL_GPL(page_poisoning_enabled);
+
+static void poison_page(struct page *page)
+{
+	void *addr = kmap_atomic(page);
+
+	/* KASAN still think the page is in-use, so skip it. */
+	kasan_disable_current();
+	memset(addr, PAGE_POISON, PAGE_SIZE);
+	kasan_enable_current();
+	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;
+
+	if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
+		return;
+
+	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))
+		pr_err("pagealloc: single bit error\n");
+	else
+		pr_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;
+
+	addr = kmap_atomic(page);
+	/*
+	 * Page poisoning when enabled poisons each and every page
+	 * that is freed to buddy. Thus no extra check is done to
+	 * see if a page was poisoned.
+	 */
+	check_poison_mem(addr, PAGE_SIZE);
+	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_poison_pages(struct page *page, int numpages, int enable)
+{
+	if (!page_poisoning_enabled())
+		return;
+
+	if (enable)
+		unpoison_pages(page, numpages);
+	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