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Date: Thu, 27 Aug 2020 00:26:55 -0500
From: "Christopher M. Riedl" <cmr@...efail.de>
To: linuxppc-dev@...ts.ozlabs.org
Cc: kernel-hardening@...ts.openwall.com
Subject: [PATCH v3 2/6] x86: Add LKDTM accessor for patching addr
When live patching a STRICT_RWX kernel, a mapping is installed at a
"patching address" with temporary write permissions. Provide a
LKDTM-only accessor function for this address in preparation for a LKDTM
test which attempts to "hijack" this mapping by writing to it from
another CPU.
Signed-off-by: Christopher M. Riedl <cmr@...efail.de>
---
arch/x86/include/asm/text-patching.h | 4 ++++
arch/x86/kernel/alternative.c | 7 +++++++
2 files changed, 11 insertions(+)
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index 6593b42cb379..f67b4dd30bf8 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -148,4 +148,8 @@ void int3_emulate_call(struct pt_regs *regs, unsigned long func)
}
#endif /* !CONFIG_UML_X86 */
+#ifdef CONFIG_LKDTM
+unsigned long read_cpu_patching_addr(unsigned int cpu);
+#endif
+
#endif /* _ASM_X86_TEXT_PATCHING_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index c3daf0aaa0ee..c16833f35a1f 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -843,6 +843,13 @@ static inline void unuse_temporary_mm(temp_mm_state_t prev_state)
__ro_after_init struct mm_struct *poking_mm;
__ro_after_init unsigned long poking_addr;
+#ifdef CONFIG_LKDTM
+unsigned long read_cpu_patching_addr(unsigned int cpu)
+{
+ return poking_addr;
+}
+#endif
+
static void *__text_poke(void *addr, const void *opcode, size_t len)
{
bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
--
2.28.0
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