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Message-Id: <20170309012456.5631-2-thgarnie@google.com>
Date: Wed, 8 Mar 2017 17:24:54 -0800
From: Thomas Garnier <thgarnie@...gle.com>
To: David Howells <dhowells@...hat.com>,
Dave Hansen <dave.hansen@...el.com>,
Arnd Bergmann <arnd@...db.de>,
Al Viro <viro@...iv.linux.org.uk>,
René Nyffenegger <mail@...enyffenegger.ch>,
Thomas Garnier <thgarnie@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
"David S . Miller" <davem@...emloft.net>,
Andy Lutomirski <luto@...nel.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Nicolas Pitre <nicolas.pitre@...aro.org>,
Petr Mladek <pmladek@...e.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
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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 v2 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 | 19 +++++++++++++++++++
arch/x86/include/asm/pgtable_64_types.h | 11 +++++++++++
arch/x86/include/asm/processor.h | 11 -----------
5 files changed, 34 insertions(+), 11 deletions(-)
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..b3527d31b91b 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -96,6 +96,19 @@ ENDPROC(native_usergs_sysret64)
# define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ
#endif
+#ifdef CONFIG_BUG_ON_DATA_CORRUPTION
+.macro VERIFY_PRE_USERMODE_STATE
+ call verify_pre_usermode_state
+.endm
+#else
+/* Similar to set_fs(USER_DS) in verify_pre_usermode_state without a warning. */
+.macro VERIFY_PRE_USERMODE_STATE
+ movq PER_CPU_VAR(current_task), %rax
+ movq $TASK_SIZE_MAX, %rcx
+ movq %rcx, TASK_addr_limit(%rax)
+.endm
+#endif
+
/*
* 64-bit SYSCALL instruction entry. Up to 6 arguments in registers.
*
@@ -201,6 +214,7 @@ 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 +232,11 @@ 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.
+ */
+ VERIFY_PRE_USERMODE_STATE
LOCKDEP_SYS_EXIT
TRACE_IRQS_ON /* user mode is traced as IRQs on */
movq RIP(%rsp), %rcx
diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
index 3a264200c62f..0fbbb79d058c 100644
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -76,4 +76,15 @@ typedef struct { pteval_t pte; } pte_t;
#define EARLY_DYNAMIC_PAGE_TABLES 64
+/*
+ * User space process size. 47bits minus one guard page. The guard
+ * page is necessary on Intel CPUs: if a SYSCALL instruction is at
+ * the highest possible canonical userspace address, then that
+ * syscall will enter the kernel with a non-canonical return
+ * address, and SYSRET will explode dangerously. We avoid this
+ * particular problem by preventing anything from being mapped
+ * at the maximum canonical address.
+ */
+#define TASK_SIZE_MAX ((_AC(1, UL) << 47) - PAGE_SIZE)
+
#endif /* _ASM_X86_PGTABLE_64_DEFS_H */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index f385eca5407a..9bc99d37133e 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -829,17 +829,6 @@ static inline void spin_lock_prefetch(const void *x)
#define KSTK_ESP(task) (task_pt_regs(task)->sp)
#else
-/*
- * User space process size. 47bits minus one guard page. The guard
- * page is necessary on Intel CPUs: if a SYSCALL instruction is at
- * the highest possible canonical userspace address, then that
- * syscall will enter the kernel with a non-canonical return
- * address, and SYSRET will explode dangerously. We avoid this
- * particular problem by preventing anything from being mapped
- * at the maximum canonical address.
- */
-#define TASK_SIZE_MAX ((1UL << 47) - PAGE_SIZE)
-
/* This decides where the kernel will search for a free chunk of vm
* space during mmap's.
*/
--
2.12.0.246.ga2ecc84866-goog
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