[PATCH 1/3] arm64: Add CONFIG_DEBUG_SET_MODULE_RONX support
Laura Abbott
lauraa at codeaurora.org
Thu Apr 17 17:47:01 PDT 2014
In a similar fashion to other architecture, add the infrastructure
and Kconfig to enable DEBUG_SET_MODULE_RONX support. When
enabled, module ranges will be marked read-only/no-execute as
appropriate.
Change-Id: I4251a0929b1fe6f43f84b14f0a64fed30769700e
Signed-off-by: Laura Abbott <lauraa at codeaurora.org>
---
arch/arm64/Kconfig.debug | 11 ++++
arch/arm64/include/asm/cacheflush.h | 4 ++
arch/arm64/mm/Makefile | 2 +-
arch/arm64/mm/pageattr.c | 120 ++++++++++++++++++++++++++++++++++++
4 files changed, 136 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/mm/pageattr.c
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index d10ec33..53979ac 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -37,4 +37,15 @@ config PID_IN_CONTEXTIDR
instructions during context switch. Say Y here only if you are
planning to use hardware trace tools with this kernel.
+config DEBUG_SET_MODULE_RONX
+ bool "Set loadable kernel module data as NX and text as RO"
+ depends on MODULES
+ help
+ This option helps catch unintended modifications to loadable
+ kernel module's text and read-only data. It also prevents execution
+ of module data. Such protection may interfere with run-time code
+ patching and dynamic kernel tracing - and they might also protect
+ against certain classes of kernel exploits.
+ If in doubt, say "N".
+
endmenu
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index 4c60e64..c12f837 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -157,4 +157,8 @@ static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
{
}
+int set_memory_ro(unsigned long addr, int numpages);
+int set_memory_rw(unsigned long addr, int numpages);
+int set_memory_x(unsigned long addr, int numpages);
+int set_memory_nx(unsigned long addr, int numpages);
#endif
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index b51d364..25b1114 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -1,5 +1,5 @@
obj-y := dma-mapping.o extable.o fault.o init.o \
cache.o copypage.o flush.o \
ioremap.o mmap.o pgd.o mmu.o \
- context.o tlb.o proc.o
+ context.o tlb.o proc.o pageattr.o
obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
new file mode 100644
index 0000000..e48f980
--- /dev/null
+++ b/arch/arm64/mm/pageattr.c
@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+static pte_t clear_pte_bit(pte_t pte, pgprot_t prot)
+{
+ pte_val(pte) &= ~pgprot_val(prot);
+ return pte;
+}
+
+static pte_t set_pte_bit(pte_t pte, pgprot_t prot)
+{
+ pte_val(pte) |= pgprot_val(prot);
+ return pte;
+}
+
+static int __change_memory(pte_t *ptep, pgtable_t token, unsigned long addr,
+ pgprot_t prot, bool set)
+{
+ pte_t pte;
+
+ if (set)
+ pte = set_pte_bit(*ptep, prot);
+ else
+ pte = clear_pte_bit(*ptep, prot);
+ set_pte(ptep, pte);
+ return 0;
+}
+
+static int set_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
+ void *data)
+{
+ pgprot_t prot = (pgprot_t)data;
+
+ return __change_memory(ptep, token, addr, prot, true);
+}
+
+static int clear_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
+ void *data)
+{
+ pgprot_t prot = (pgprot_t)data;
+
+ return __change_memory(ptep, token, addr, prot, false);
+}
+
+static int change_memory_common(unsigned long addr, int numpages,
+ pgprot_t prot, bool set)
+{
+ unsigned long start = addr;
+ unsigned long size = PAGE_SIZE*numpages;
+ unsigned long end = start + size;
+ int ret;
+
+ if (start < MODULES_VADDR || start >= MODULES_END)
+ return -EINVAL;
+
+ if (end < MODULES_VADDR || end >= MODULES_END)
+ return -EINVAL;
+
+ if (set)
+ ret = apply_to_page_range(&init_mm, start, size,
+ set_page_range, (void *)prot);
+ else
+ ret = apply_to_page_range(&init_mm, start, size,
+ clear_page_range, (void *)prot);
+
+ flush_tlb_kernel_range(start, end);
+ return ret;
+}
+
+static int change_memory_set_bit(unsigned long addr, int numpages,
+ pgprot_t prot)
+{
+ return change_memory_common(addr, numpages, prot, true);
+}
+
+static int change_memory_clear_bit(unsigned long addr, int numpages,
+ pgprot_t prot)
+{
+ return change_memory_common(addr, numpages, prot, false);
+}
+
+int set_memory_ro(unsigned long addr, int numpages)
+{
+ return change_memory_set_bit(addr, numpages, __pgprot(PTE_RDONLY));
+}
+EXPORT_SYMBOL_GPL(set_memory_ro);
+
+int set_memory_rw(unsigned long addr, int numpages)
+{
+ return change_memory_clear_bit(addr, numpages, __pgprot(PTE_RDONLY));
+}
+EXPORT_SYMBOL_GPL(set_memory_rw);
+
+int set_memory_nx(unsigned long addr, int numpages)
+{
+ return change_memory_set_bit(addr, numpages, __pgprot(PTE_PXN));
+}
+EXPORT_SYMBOL_GPL(set_memory_nx);
+
+int set_memory_x(unsigned long addr, int numpages)
+{
+ return change_memory_clear_bit(addr, numpages, __pgprot(PTE_PXN));
+}
+EXPORT_SYMBOL_GPL(set_memory_x);
--
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