[PATCH v8 4/4] arm64/syscalls: Optimize address limit check
From: Thomas Garnier <hidden>
Date: 2017-04-26 18:35:10
Also in:
linux-arm-kernel, linux-s390, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
Disable the generic address limit check in favor of an architecture specific optimized implementation. The address limit is checked on each syscall return path to user-mode. If it was changed, a generic handler is called to stop the kernel on an explicit check. Signed-off-by: Thomas Garnier <redacted> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> --- Based on next-20170426 --- arch/arm64/Kconfig | 1 + arch/arm64/kernel/entry.S | 12 ++++++++++++ 2 files changed, 13 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 3dcd7ec69bca..fe9466d3bf94 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig@@ -25,6 +25,7 @@ config ARM64 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION select ARCH_WANT_FRAME_POINTERS select ARCH_HAS_UBSAN_SANITIZE_ALL + select ADDR_LIMIT_CHECK select ARM_AMBA select ARM_ARCH_TIMER select ARM_GIC
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 43512d4d7df2..c895c4402d32 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S@@ -744,6 +744,8 @@ ENDPROC(cpu_switch_to) ret_fast_syscall: disable_irq // disable interrupts str x0, [sp, #S_X0] // returned x0 + ldr x2, [tsk, #TSK_TI_ADDR_LIMIT] // check addr limit change + tbnz x2, #63, addr_limit_fail ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing and x2, x1, #_TIF_SYSCALL_WORK cbnz x2, ret_fast_syscall_trace
@@ -771,6 +773,8 @@ work_pending: */ ret_to_user: disable_irq // disable interrupts + ldr x2, [tsk, #TSK_TI_ADDR_LIMIT] // check addr limit change + tbnz x2, #63, addr_limit_fail ldr x1, [tsk, #TSK_TI_FLAGS] and x2, x1, #_TIF_WORK_MASK cbnz x2, work_pending
@@ -780,6 +784,14 @@ finish_ret_to_user: ENDPROC(ret_to_user) /* + * Address limit was incorrect before returning in user-mode which could be + * used to elevate privileges. Call the generic handler to stop the kernel on + * the appropriate check. This function does not return. + */ +addr_limit_fail: + b addr_limit_check_failed + +/* * This is how we return from a fork. */ ENTRY(ret_from_fork)
--
2.13.0.rc0.306.g87b477812d-goog