[PATCH v2 2/3] extable: verify address is read-only

From: Eddie Kovsky
Date: Sat Feb 18 2017 - 01:07:59 EST


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@xxxxxxxxxxxx>
---
include/linux/kernel.h | 2 ++
kernel/extable.c | 29 +++++++++++++++++++++++++++++
2 files changed, 31 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..e9608f129730 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -149,3 +149,32 @@ 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;
+
+ return 0;
+}
--
2.11.1