From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Garnier Subject: Re: [PATCH v3 3/4] arm/syscalls: Optimize address limit check Date: Tue, 29 Aug 2017 07:32:39 -0700 Message-ID: References: <20170814213732.104301-1-thgarnie@google.com> <20170814213732.104301-3-thgarnie@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Al Viro , Dave Hansen , Arnd Bergmann , Thomas Gleixner , Thomas Garnier , Yonghong Song , David Howells , Russell King , Kees Cook , Andy Lutomirski , Will Drewry , Dave Martin , Catalin Marinas , Will Deacon Cc: Linux API , LKML , Linux ARM , Kernel Hardening , =?UTF-8?Q?Lothar_Wa=C3=9Fmann?= List-Id: linux-api@vger.kernel.org On Tue, Aug 22, 2017 at 9:42 AM, Thomas Garnier wrote: > On Mon, Aug 14, 2017 at 2:37 PM, Thomas Garnier wrote: >> 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. >> >> Signed-off-by: Thomas Garnier > > Any feedback? CCing LW-AvR2QvxeiV7DiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org who experienced the same issue this patch proposal fix. Russel: Any feedback? > >> --- >> arch/arm/kernel/entry-common.S | 11 +++++++++++ >> arch/arm/kernel/signal.c | 7 +++++++ >> 2 files changed, 18 insertions(+) >> >> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S >> index 0b60adf4a5d9..99c908226065 100644 >> --- a/arch/arm/kernel/entry-common.S >> +++ b/arch/arm/kernel/entry-common.S >> @@ -12,6 +12,7 @@ >> #include >> #include >> #include >> +#include >> #ifdef CONFIG_AEABI >> #include >> #endif >> @@ -48,10 +49,14 @@ 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 >> >> + >> /* perform architecture specific actions before user return */ >> arch_ret_to_user r1, lr >> >> @@ -74,6 +79,9 @@ 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 >> @@ -106,6 +114,9 @@ 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 5814298ef0b7..b67ae12503f3 100644 >> --- a/arch/arm/kernel/signal.c >> +++ b/arch/arm/kernel/signal.c >> @@ -14,6 +14,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include >> @@ -673,3 +674,9 @@ struct page *get_signal_page(void) >> >> return page; >> } >> + >> +/* Defer to generic check */ >> +asmlinkage void addr_limit_check_failed(void) >> +{ >> + addr_limit_user_check(); >> +} >> -- >> 2.14.1.480.gb18f417b89-goog >> > > > > -- > Thomas -- Thomas