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Date: Sun, 12 Feb 2017 16:31:40 -0700
From: Eddie Kovsky <ewk@...ovsky.org>
To: jeyu@...hat.com,
rusty@...tcorp.com.au,
keescook@...omium.org
Cc: kernel-hardening@...ts.openwall.com,
Eddie Kovsky <ewk@...ovsky.org>
Subject: [RFC] [PATCH 2/2] extable: verify address is read-only
Provide a mechanism to check if the address of a variable is
const or ro_after_init. It mimics the existing functions that test if an
address is inside the kernel's text section.
Signed-off-by: Eddie Kovsky <ewk@...ovsky.org>
---
include/linux/kernel.h | 2 ++
kernel/extable.c | 31 +++++++++++++++++++++++++++++++
2 files changed, 33 insertions(+)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 4c26dc3a8295..51beea39e6c4 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -444,6 +444,8 @@ extern int core_kernel_data(unsigned long addr);
extern int __kernel_text_address(unsigned long addr);
extern int kernel_text_address(unsigned long addr);
extern int func_ptr_is_kernel_text(void *ptr);
+extern int core_kernel_ro_data(unsigned long addr);
+extern int kernel_ro_address(unsigned long addr);
unsigned long int_sqrt(unsigned long);
diff --git a/kernel/extable.c b/kernel/extable.c
index 6b0d09051efb..f5a29c4ae391 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -149,3 +149,34 @@ int func_ptr_is_kernel_text(void *ptr)
return 1;
return is_module_text_address(addr);
}
+
+/**
+ * core_kernel_ro_data - Verify address points to read-only section
+ * @addr: address to test
+ *
+ */
+int core_kernel_ro_data(unsigned long addr)
+{
+ if (addr >= (unsigned long)__start_rodata &&
+ addr < (unsigned long)__end_rodata)
+ return 1;
+
+ if (addr >= (unsigned long)__start_data_ro_after_init &&
+ addr < (unsigned long)__end_data_ro_after_init)
+ return 1;
+
+ return 0;
+}
+
+/* Verify that address is const or ro_after_init. */
+int kernel_ro_address(unsigned long addr)
+{
+ if (core_kernel_ro_data(addr))
+ return 1;
+ if (is_module_ro_address(addr))
+ return 1;
+ if (is_ftrace_trampoline(addr))
+ return 1;
+
+ return 0;
+}
--
2.11.1
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