From a8368c98150273e6d5c6137c5656a979b98c58a6 Mon Sep 17 00:00:00 2001
From: Thomas Garnier <thgarnie@google.com>
Date: Thu, 7 Sep 2017 08:30:46 -0700
Subject: [PATCH] BACKPORT: arm/syscalls: Optimize address limit check
(cherry-picked from e33f8d32677fa4f4f8996ef46748f86aac81ccff)
Disable the generic address limit check in favor of an architecture
specific optimized implementation. The generic implementation using
pending work flags did not work well with ARM and alignment faults.
The address limit is checked on each syscall return path to user-mode
path as well as the irq user-mode return function. If the address limit
was changed, a function is called to report data corruption (stopping
the kernel or process based on configuration).
The address limit check has to be done before any pending work because
they can reset the address limit and the process is killed using a
SIGKILL signal. For example the lkdtm address limit check does not work
because the signal to kill the process will reset the user-mode address
limit.
Change-Id: Ic61ba05961ad1dcf10c48040427d92bd650616af
Signed-off-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Pratyush Anand <panand@redhat.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: Will Drewry <wad@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-api@vger.kernel.org
Cc: Yonghong Song <yhs@fb.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1504798247-48833-4-git-send-email-keescook@chromium.org
Signed-off-by: Satya Tangirala <satyat@google.com>
---
arch/arm/kernel/entry-common.S | 10 ++++++++++
arch/arm/kernel/signal.c | 7 +++++++
2 files changed, 17 insertions(+)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 30a7228eaceb..9440b320a8a3 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -12,6 +12,7 @@
#include <asm/unistd.h>
#include <asm/ftrace.h>
#include <asm/unwind.h>
+#include <asm/memory.h>
#ifdef CONFIG_NEED_RET_TO_USER
#include <mach/entry-macro.S>
@@ -35,6 +36,9 @@ ret_fast_syscall:
UNWIND(.fnstart )
UNWIND(.cantunwind )
disable_irq_notrace @ disable interrupts
+ ldr r2, [tsk, #TI_ADDR_LIMIT]
+ cmp r2, #TASK_SIZE
+ blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
bne fast_work_pending
@@ -61,6 +65,9 @@ ret_fast_syscall:
UNWIND(.cantunwind )
str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
disable_irq_notrace @ disable interrupts
+ ldr r2, [tsk, #TI_ADDR_LIMIT]
+ cmp r2, #TASK_SIZE
+ blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
beq no_work_pending
@@ -93,6 +100,9 @@ ENTRY(ret_to_user)
ret_slow_syscall:
disable_irq_notrace @ disable interrupts
ENTRY(ret_to_user_from_irq)
+ ldr r2, [tsk, #TI_ADDR_LIMIT]
+ cmp r2, #TASK_SIZE
+ blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS]
tst r1, #_TIF_WORK_MASK
bne slow_work_pending
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 7b8f2141427b..304e68408f9c 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -14,6 +14,7 @@
#include <linux/uaccess.h>
#include <linux/tracehook.h>
#include <linux/uprobes.h>
+#include <linux/syscalls.h>
#include <asm/elf.h>
#include <asm/cacheflush.h>
@@ -631,3 +632,9 @@ struct page *get_signal_page(void)
return page;
}
+
+/* Defer to generic check */
+asmlinkage void addr_limit_check_failed(void)
+{
+ addr_limit_user_check();
+}