linux-kernel - [PATCH v1 2/4] x86/syscalls: Specific usage of verify_pre_usermode

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Date:   Wed,  8 Mar 2017 13:38:42 -0800
From:   Thomas Garnier <thgarnie@...gle.com>
To:     Arnd Bergmann <arnd@...db.de>, David Howells <dhowells@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Dave Hansen <dave.hansen@...el.com>,
        Thomas Garnier <thgarnie@...gle.com>,
        René Nyffenegger <mail@...enyffenegger.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Petr Mladek <pmladek@...e.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Helge Deller <deller@....de>, Rik van Riel <riel@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Oleg Nesterov <oleg@...hat.com>,
        Stanislav Kinsburskiy <skinsbursky@...tuozzo.com>,
        Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        Borislav Petkov <bp@...en8.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Brian Gerst <brgerst@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Jan Beulich <JBeulich@...e.com>,
        Russell King <linux@...linux.org.uk>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Laura Abbott <labbott@...hat.com>,
        Andre Przywara <andre.przywara@....com>
Cc:     linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-hardening@...ts.openwall.com
Subject: [PATCH v1 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state

Implement specific usage of verify_pre_usermode_state for user-mode
returns for x86.
---
Based on next-20170308
---
 arch/x86/Kconfig          | 1 +
 arch/x86/entry/common.c   | 3 +++
 arch/x86/entry/entry_64.S | 6 ++++++
 3 files changed, 10 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 005df7c825f5..6d48e18e6f09 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -63,6 +63,7 @@ config X86
 	select ARCH_MIGHT_HAVE_ACPI_PDC		if ACPI
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
+	select ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 	select ARCH_SUPPORTS_NUMA_BALANCING	if X86_64
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 370c42c7f046..525edbb77f03 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -22,6 +22,7 @@
 #include <linux/context_tracking.h>
 #include <linux/user-return-notifier.h>
 #include <linux/uprobes.h>
+#include <linux/syscalls.h>
 
 #include <asm/desc.h>
 #include <asm/traps.h>
@@ -180,6 +181,8 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
 	struct thread_info *ti = current_thread_info();
 	u32 cached_flags;
 
+	verify_pre_usermode_state();
+
 	if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled()))
 		local_irq_disable();
 
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d2b2a2948ffe..795c31eebd09 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -201,6 +201,7 @@ entry_SYSCALL_64_fastpath:
 	 * It might end up jumping to the slow path.  If it jumps, RAX
 	 * and all argument registers are clobbered.
 	 */
+
 	call	*sys_call_table(, %rax, 8)
 .Lentry_SYSCALL_64_after_fastpath_call:
 
@@ -218,6 +219,11 @@ entry_SYSCALL_64_fastpath:
 	testl	$_TIF_ALLWORK_MASK, TASK_TI_flags(%r11)
 	jnz	1f
 
+	/*
+	 * Check user-mode state on fast path return, the same check is done
+	 * under the slow path through syscall_return_slowpath.
+	 */
+	call	verify_pre_usermode_state
 	LOCKDEP_SYS_EXIT
 	TRACE_IRQS_ON		/* user mode is traced as IRQs on */
 	movq	RIP(%rsp), %rcx
-- 
2.12.0.246.ga2ecc84866-goog