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From: Amit Daniel Kachhap <amit.kachhap@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	Kristina Martsenko <kristina.martsenko@arm.com>,
	James Morse <james.morse@arm.com>,
	Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
	Amit Daniel Kachhap <amit.kachhap@arm.com>,
	Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
	Dave Martin <Dave.Martin@arm.com>
Subject: [PATCH 08/11] arm64: unwind: strip PAC from kernel addresses
Date: Thu, 17 Oct 2019 13:44:22 +0530	[thread overview]
Message-ID: <1571300065-10236-9-git-send-email-amit.kachhap@arm.com> (raw)
In-Reply-To: <1571300065-10236-1-git-send-email-amit.kachhap@arm.com>

From: Kristina Martsenko <kristina.martsenko@arm.com>

When we enable pointer authentication in the kernel, LR values saved to
the stack will have a PAC which we must strip in order to retrieve the
real return address.

Strip PACs when unwinding the stack in order to account for this.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
Changes since RFC v2:
 - None

 arch/arm64/include/asm/pointer_auth.h | 9 ++++++---
 arch/arm64/kernel/stacktrace.c        | 3 +++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 599dd09..a75dc89 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -59,12 +59,15 @@ extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
  * The EL0 pointer bits used by a pointer authentication code.
  * This is dependent on TBI0 being enabled, or bits 63:56 would also apply.
  */
-#define ptrauth_user_pac_mask()	GENMASK(54, vabits_actual)
+#define ptrauth_user_pac_mask()		GENMASK(54, vabits_actual)
+#define ptrauth_kernel_pac_mask()	(GENMASK(63, 56) | GENMASK(54, VA_BITS))
 
-/* Only valid for EL0 TTBR0 instruction pointers */
 static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 {
-	return ptr & ~ptrauth_user_pac_mask();
+	if (ptr & BIT_ULL(55))
+		return ptr | ptrauth_kernel_pac_mask();
+	else
+		return ptr & ~ptrauth_user_pac_mask();
 }
 
 #define ptrauth_thread_init_user(tsk)					\
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index a336cb1..49eb1c3 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -14,6 +14,7 @@
 #include <linux/stacktrace.h>
 
 #include <asm/irq.h>
+#include <asm/pointer_auth.h>
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
 
@@ -84,6 +85,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 	frame->prev_fp = fp;
 	frame->prev_type = info.type;
 
+	frame->pc = ptrauth_strip_insn_pac(frame->pc);
+
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	if (tsk->ret_stack &&
 			(frame->pc == (unsigned long)return_to_handler)) {
-- 
2.7.4


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  parent reply	other threads:[~2019-10-17  8:17 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17  8:14 [PATCH 00/11] arm64: return address signing Amit Daniel Kachhap
2019-10-17  8:14 ` [PATCH 01/11] arm64: cpufeature: add pointer auth meta-capabilities Amit Daniel Kachhap
2019-10-17  8:14 ` [PATCH 02/11] arm64: install user ptrauth keys at kernel exit time Amit Daniel Kachhap
2019-10-17  8:14 ` [PATCH 03/11] arm64: cpufeature: handle conflicts based on capability Amit Daniel Kachhap
2019-10-17 14:06   ` Suzuki K Poulose
2019-10-18  9:59     ` Amit Kachhap
2019-10-17  8:14 ` [PATCH 04/11] arm64: create macro to park cpu in an infinite loop Amit Daniel Kachhap
2019-10-17  8:14 ` [PATCH 05/11] arm64: enable ptrauth earlier Amit Daniel Kachhap
2019-10-17 14:13   ` Suzuki K Poulose
2019-10-18 10:07     ` Amit Kachhap
2019-10-23 17:32   ` James Morse
2019-10-30  4:01     ` Amit Daniel Kachhap
2019-10-17  8:14 ` [PATCH 06/11] arm64: rename ptrauth key structures to be user-specific Amit Daniel Kachhap
2019-10-29 23:27   ` Kees Cook
2019-10-17  8:14 ` [PATCH 07/11] arm64: initialize and switch ptrauth kernel keys Amit Daniel Kachhap
2019-10-23 17:35   ` James Morse
2019-10-30  4:02     ` Amit Daniel Kachhap
2019-10-17  8:14 ` Amit Daniel Kachhap [this message]
2019-10-23 17:36   ` [PATCH 08/11] arm64: unwind: strip PAC from kernel addresses James Morse
2019-10-30  4:02     ` Amit Daniel Kachhap
2019-10-17  8:14 ` [RFC PATCH 09/11] arm64: suspend: restore the kernel ptrauth keys Amit Daniel Kachhap
2019-10-17  8:14 ` [RFC PATCH 10/11] arm64: mask PAC bits of __builtin_return_address Amit Daniel Kachhap
2019-10-17  8:14 ` [PATCH 11/11] arm64: compile the kernel with ptrauth return address signing Amit Daniel Kachhap
2019-10-23 17:31 ` [PATCH 00/11] arm64: " James Morse
2019-10-30  3:59   ` Amit Daniel Kachhap

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