[PATCH v1 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state

Thomas Garnier
2017-03-08T21:38:42Z

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