Subject: [PATCH v6 11/18] arm64: initialize ptrauth keys for kernel booting task

From: Amit Daniel Kachhap <[email-masked]>
Date: Fri, 6 Mar 2020 12:05:18 +0530

This patch uses the existing boot_init_stack_canary arch function
to initialize the ptrauth keys for the booting task in the primary
core. The requirement here is that it should be always inline and
the caller must never return.

As pointer authentication too detects a subset of stack corruption
so it makes sense to place this code here.

Both pointer authentication and stack canary codes are protected
by their respective config option.

Suggested-by: Ard Biesheuvel <[email-masked]>
Reviewed-by: Catalin Marinas <[email-masked]>
Signed-off-by: Amit Daniel Kachhap <[email-masked]>
---
 arch/arm64/include/asm/pointer_auth.h   | 11 ++++++++++-
 arch/arm64/include/asm/stackprotector.h |  5 +++++
 include/linux/stackprotector.h          |  2 +-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index aa956ca..833d3f9 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -54,12 +54,18 @@ do {								\
 	write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1);	\
 } while (0)
 
-static inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
+static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
 {
 	if (system_supports_address_auth())
 		get_random_bytes(&keys->apia, sizeof(keys->apia));
 }
 
+static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
+{
+	if (system_supports_address_auth())
+		__ptrauth_key_install(APIA, keys->apia);
+}
+
 extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
 
 /*
@@ -78,12 +84,15 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 	ptrauth_keys_init_user(&(tsk)->thread.keys_user)
 #define ptrauth_thread_init_kernel(tsk)					\
 	ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel)
+#define ptrauth_thread_switch_kernel(tsk)				\
+	ptrauth_keys_switch_kernel(&(tsk)->thread.keys_kernel)
 
 #else /* CONFIG_ARM64_PTR_AUTH */
 #define ptrauth_prctl_reset_keys(tsk, arg)	(-EINVAL)
 #define ptrauth_strip_insn_pac(lr)	(lr)
 #define ptrauth_thread_init_user(tsk)
 #define ptrauth_thread_init_kernel(tsk)
+#define ptrauth_thread_switch_kernel(tsk)
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
 #endif /* __ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h
index 5884a2b..7263e0b 100644
--- a/arch/arm64/include/asm/stackprotector.h
+++ b/arch/arm64/include/asm/stackprotector.h
@@ -15,6 +15,7 @@
 
 #include <linux/random.h>
 #include <linux/version.h>
+#include <asm/pointer_auth.h>
 
 extern unsigned long __stack_chk_guard;
 
@@ -26,6 +27,7 @@ extern unsigned long __stack_chk_guard;
  */
 static __always_inline void boot_init_stack_canary(void)
 {
+#if defined(CONFIG_STACKPROTECTOR)
 	unsigned long canary;
 
 	/* Try to get a semi random initial value. */
@@ -36,6 +38,9 @@ static __always_inline void boot_init_stack_canary(void)
 	current->stack_canary = canary;
 	if (!IS_ENABLED(CONFIG_STACKPROTECTOR_PER_TASK))
 		__stack_chk_guard = current->stack_canary;
+#endif
+	ptrauth_thread_init_kernel(current);
+	ptrauth_thread_switch_kernel(current);
 }
 
 #endif	/* _ASM_STACKPROTECTOR_H */
diff --git a/include/linux/stackprotector.h b/include/linux/stackprotector.h
index 6b792d0..4c678c4 100644
--- a/include/linux/stackprotector.h
+++ b/include/linux/stackprotector.h
@@ -6,7 +6,7 @@
 #include <linux/sched.h>
 #include <linux/random.h>
 
-#ifdef CONFIG_STACKPROTECTOR
+#if defined(CONFIG_STACKPROTECTOR) || defined(CONFIG_ARM64_PTR_AUTH)
 # include <asm/stackprotector.h>
 #else
 static inline void boot_init_stack_canary(void)
-- 
2.7.4

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