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From: Kees Cook <keescook@chromium.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>,
	Elena Reshetova <elena.reshetova@intel.com>,
	x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Potapenko <glider@google.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jann Horn <jannh@google.com>,
	"Perla, Enrico" <enrico.perla@intel.com>,
	kernel-hardening@lists.openwall.com,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2 5/5] arm64: entry: Enable random_kstack_offset support
Date: Tue, 24 Mar 2020 13:32:31 -0700	[thread overview]
Message-ID: <20200324203231.64324-6-keescook@chromium.org> (raw)
In-Reply-To: <20200324203231.64324-1-keescook@chromium.org>

Allow for a randomized stack offset on a per-syscall basis, with roughly
5 bits of entropy.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/Kconfig          |  1 +
 arch/arm64/kernel/syscall.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0b30e884e088..4d5aa4959f72 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -127,6 +127,7 @@ config ARM64
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
 	select HAVE_ARCH_PREL32_RELOCATIONS
+	select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_STACKLEAK
 	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index a12c0c88d345..238dbd753b44 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -5,6 +5,7 @@
 #include <linux/errno.h>
 #include <linux/nospec.h>
 #include <linux/ptrace.h>
+#include <linux/randomize_kstack.h>
 #include <linux/syscalls.h>
 
 #include <asm/daifflags.h>
@@ -42,6 +43,8 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 {
 	long ret;
 
+	add_random_kstack_offset();
+
 	if (scno < sc_nr) {
 		syscall_fn_t syscall_fn;
 		syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
@@ -51,6 +54,13 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 	}
 
 	regs->regs[0] = ret;
+
+	/*
+	 * Since the compiler chooses a 4 bit alignment for the stack,
+	 * let's save one additional bit (9 total), which gets us up
+	 * near 5 bits of entropy.
+	 */
+	choose_random_kstack_offset(get_random_int() & 0x1FF);
 }
 
 static inline bool has_syscall_work(unsigned long flags)
-- 
2.20.1


WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Alexander Potapenko <glider@google.com>,
	linux-arm-kernel@lists.infradead.org,
	Andy Lutomirski <luto@kernel.org>,
	kernel-hardening@lists.openwall.com, "Perla,
	Enrico" <enrico.perla@intel.com>, Will Deacon <will@kernel.org>,
	Elena Reshetova <elena.reshetova@intel.com>
Subject: [PATCH v2 5/5] arm64: entry: Enable random_kstack_offset support
Date: Tue, 24 Mar 2020 13:32:31 -0700	[thread overview]
Message-ID: <20200324203231.64324-6-keescook@chromium.org> (raw)
In-Reply-To: <20200324203231.64324-1-keescook@chromium.org>

Allow for a randomized stack offset on a per-syscall basis, with roughly
5 bits of entropy.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/Kconfig          |  1 +
 arch/arm64/kernel/syscall.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0b30e884e088..4d5aa4959f72 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -127,6 +127,7 @@ config ARM64
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
 	select HAVE_ARCH_PREL32_RELOCATIONS
+	select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_STACKLEAK
 	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index a12c0c88d345..238dbd753b44 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -5,6 +5,7 @@
 #include <linux/errno.h>
 #include <linux/nospec.h>
 #include <linux/ptrace.h>
+#include <linux/randomize_kstack.h>
 #include <linux/syscalls.h>
 
 #include <asm/daifflags.h>
@@ -42,6 +43,8 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 {
 	long ret;
 
+	add_random_kstack_offset();
+
 	if (scno < sc_nr) {
 		syscall_fn_t syscall_fn;
 		syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
@@ -51,6 +54,13 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 	}
 
 	regs->regs[0] = ret;
+
+	/*
+	 * Since the compiler chooses a 4 bit alignment for the stack,
+	 * let's save one additional bit (9 total), which gets us up
+	 * near 5 bits of entropy.
+	 */
+	choose_random_kstack_offset(get_random_int() & 0x1FF);
 }
 
 static inline bool has_syscall_work(unsigned long flags)
-- 
2.20.1


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  parent reply	other threads:[~2020-03-24 20:32 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 20:32 [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-24 20:32 ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 1/5] jump_label: Provide CONFIG-driven build state defaults Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-24 22:06   ` Peter Zijlstra
2020-03-24 22:06     ` Peter Zijlstra
2020-03-24 20:32 ` [PATCH v2 2/5] init_on_alloc: Unpessimize default-on builds Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-26 15:48   ` Alexander Potapenko
2020-03-26 15:48     ` Alexander Potapenko
2020-03-26 15:48     ` Alexander Potapenko
2020-03-24 20:32 ` [PATCH v2 3/5] stack: Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-30 11:25   ` Mark Rutland
2020-03-30 11:25     ` Mark Rutland
2020-03-30 18:18     ` Kees Cook
2020-03-30 18:18       ` Kees Cook
2020-03-30 18:27     ` Kees Cook
2020-03-30 18:27       ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 4/5] x86/entry: Enable random_kstack_offset support Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-28 22:26   ` Kees Cook
2020-03-28 22:26     ` Kees Cook
2020-03-24 20:32 ` Kees Cook [this message]
2020-03-24 20:32   ` [PATCH v2 5/5] arm64: entry: " Kees Cook
2020-03-25 13:21   ` Mark Rutland
2020-03-25 13:21     ` Mark Rutland
2020-03-25 20:22     ` Kees Cook
2020-03-25 20:22       ` Kees Cook
2020-03-26 11:15       ` Mark Rutland
2020-03-26 11:15         ` Mark Rutland
2020-03-26 16:31         ` Kees Cook
2020-03-26 16:31           ` Kees Cook
2020-03-30 11:26           ` Mark Rutland
2020-03-30 11:26             ` Mark Rutland
2020-04-20 20:54   ` Will Deacon
2020-04-20 20:54     ` Will Deacon
2020-04-20 22:34     ` Kees Cook
2020-04-20 22:34       ` Kees Cook
2020-04-21  7:02       ` Will Deacon
2020-04-21  7:02         ` Will Deacon
2020-03-24 21:28 ` [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Jann Horn
2020-03-24 21:28   ` Jann Horn
2020-03-24 21:28   ` Jann Horn
2020-03-24 23:07   ` Kees Cook
2020-03-24 23:07     ` Kees Cook
2020-03-25 12:15     ` Reshetova, Elena
2020-03-25 12:15       ` Reshetova, Elena
2020-03-25 12:15       ` Reshetova, Elena
2020-03-25 20:27       ` Kees Cook
2020-03-25 20:27         ` Kees Cook
2020-03-25 20:27         ` Kees Cook
2020-03-25 23:20         ` Jann Horn
2020-03-25 23:20           ` Jann Horn
2020-03-25 23:20           ` Jann Horn
2020-03-26 17:18           ` Kees Cook
2020-03-26 17:18             ` Kees Cook
2020-03-26 17:18             ` Kees Cook

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