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Thu, 19 Jul 2018 03:41:17 -0700 (PDT) Received: from [192.168.42.175] ([213.87.144.170]) by smtp.gmail.com with ESMTPSA id o62-v6sm903176lfe.71.2018.07.19.03.41.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 19 Jul 2018 03:41:17 -0700 (PDT) Reply-To: alex.popov@linux.com Subject: Re: [PATCH 2/2] arm64: Clear the stack To: Laura Abbott , Kees Cook , Mark Rutland , Ard Biesheuvel Cc: kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Will Deacon , Catalin Marinas References: <20180718211013.14512-1-labbott@redhat.com> <20180718211013.14512-3-labbott@redhat.com> From: Alexander Popov Openpgp: preference=signencrypt Autocrypt: addr=alex.popov@linux.com; prefer-encrypt=mutual; keydata= xsFNBFX15q4BEADZartsIW3sQ9R+9TOuCFRIW+RDCoBWNHhqDLu+Tzf2mZevVSF0D5AMJW4f UB1QigxOuGIeSngfmgLspdYe2Kl8+P8qyfrnBcS4hLFyLGjaP7UVGtpUl7CUxz2Hct3yhsPz ID/rnCSd0Q+3thrJTq44b2kIKqM1swt/F2Er5Bl0B4o5WKx4J9k6Dz7bAMjKD8pHZJnScoP4 dzKPhrytN/iWM01eRZRc1TcIdVsRZC3hcVE6OtFoamaYmePDwWTRhmDtWYngbRDVGe3Tl8bT 7BYN7gv7Ikt7Nq2T2TOfXEQqr9CtidxBNsqFEaajbFvpLDpUPw692+4lUbQ7FL0B1WYLvWkG cVysClEyX3VBSMzIG5eTF0Dng9RqItUxpbD317ihKqYL95jk6eK6XyI8wVOCEa1V3MhtvzUo WGZVkwm9eMVZ05GbhzmT7KHBEBbCkihS+TpVxOgzvuV+heCEaaxIDWY/k8u4tgbrVVk+tIVG 99v1//kNLqd5KuwY1Y2/h2MhRrfxqGz+l/f/qghKh+1iptm6McN//1nNaIbzXQ2Ej34jeWDa xAN1C1OANOyV7mYuYPNDl5c9QrbcNGg3D6gOeGeGiMn11NjbjHae3ipH8MkX7/k8pH5q4Lhh Ra0vtJspeg77CS4b7+WC5jlK3UAKoUja3kGgkCrnfNkvKjrkEwARAQABzSZBbGV4YW5kZXIg UG9wb3YgPGFsZXgucG9wb3ZAbGludXguY29tPsLBgAQTAQoAKgIbIwIeAQIXgAULCQgHAwUV CgkICwUWAgMBAAUJB8+UXAUCWgsUegIZAQAKCRCODp3rvH6PqqpOEACX+tXHOgMJ6fGxaNJZ HkKRFR/9AGP1bxp5QS528Sd6w17bMMQ87V5NSFUsTMPMcbIoO73DganKQ3nN6tW0ZvDTKpRt pBUCUP8KPqNvoSs3kkskaQgNQ3FXv46YqPZ7DoYj9HevY9NUyGLwCTEWD2ER5zKuNbI2ek82 j4rwdqXn9kqqBf1ExAoEsszeNHzTKRl2d+bXuGDcOdpnOi7avoQfwi/O0oapR+goxz49Oeov YFf1EVaogHjDBREaqiqJ0MSKexfVBt8RD9ev9SGSIMcwfhgUHhMTX2JY/+6BXnUbzVcHD6HR EgqVGn/0RXfJIYmFsjH0Z6cHy34Vn+aqcGa8faztPnmkA/vNfhw8k5fEE7VlBqdEY8YeOiza hHdpaUi4GofNy/GoHIqpz16UulMjGB5SBzgsYKgCO+faNBrCcBrscWTl1aJfSNJvImuS1JhB EQnl/MIegxyBBRsH68x5BCffERo4FjaG0NDCmZLjXPOgMvl3vRywHLdDZThjAea3pwdGUq+W C77i7tnnUqgK7P9i+nEKwNWZfLpfjYgH5JE/jOgMf4tpHvO6fu4AnOffdz3kOxDyi+zFLVcz rTP5b46aVjI7D0dIDTIaCKUT+PfsLnJmP18x7dU/gR/XDcUaSEbWU3D9u61AvxP47g7tN5+a 5pFIJhJ44JLk6I5H/c7BTQRV9eauARAArcUVf6RdT14hkm0zT5TPc/3BJc6PyAghV/iCoPm8 kbzjKBIK80NvGodDeUV0MnQbX40jjFdSI0m96HNt86FtifQ3nwuW/BtS8dk8+lakRVwuTgMb hJWmXqKMFdVRCbjdyLbZWpdPip0WGND6p5i801xgPRmI8P6e5e4jBO4Cx1ToIFyJOzD/jvtb UhH9t5/naKUGa5BD9gSkguooXVOFvPdvKQKca19S7bb9hzjySh63H4qlbhUrG/7JGhX+Lr3g DwuAGrrFIV0FaVyIPGZ8U2fjLKpcBC7/lZJv0jRFpZ9CjHefILxt7NGxPB9hk2iDt2tE6jSl GNeloDYJUVItFmG+/giza2KrXmDEFKl+/mwfjRI/+PHR8PscWiB7S1zhsVus3DxhbM2mAK4x mmH4k0wNfgClh0Srw9zCU2CKJ6YcuRLi/RAAiyoxBb9wnSuQS5KkxoT32LRNwfyMdwlEtQGp WtC/vBI13XJVabx0Oalx7NtvRCcX1FX9rnKVjSFHX5YJ48heAd0dwRVmzOGL/EGywb1b9Q3O IWe9EFF8tmWV/JHs2thMz492qTHA5pm5JUsHQuZGBhBU+GqdOkdkFvujcNu4w7WyuEITBFAh 5qDiGkvY9FU1OH0fWQqVU/5LHNizzIYN2KjU6529b0VTVGb4e/M0HglwtlWpkpfQzHMAEQEA AcLBZQQYAQIADwUCVfXmrgIbDAUJCWYBgAAKCRCODp3rvH6PqrZtEACKsd/UUtpKmy4mrZwl 053nWp7+WCE+S9ke7CFytmXoMWf1CIrcQTk5cmdBmB4E0l3sr/DgKlJ8UrHTdRLcZZnbVqur +fnmVeQy9lqGkaIZvx/iXVYUqhT3+DNj9Zkjrynbe5pLsrGyxYWfsPRVL6J4mQatChadjuLw 7/WC6PBmWkRA2SxUVpxFEZlirpbboYWLSXk9I3JmS5/iJ+P5kHYiB0YqYkd1twFXXxixv1GB Zi/idvWTK7x6/bUh0AAGTKc5zFhyR4DJRGROGlFTAYM3WDoa9XbrHXsggJDLNoPZJTj9DMww u28SzHLvR3t2pY1dT61jzKNDLoE3pjvzgLKF/Olif0t7+m0IPKY+8umZvUEhJ9CAUcoFPCfG tEbL6t1xrcsT7dsUhZpkIX0Qc77op8GHlfNd/N6wZUt19Vn9G8B6xrH+dinc0ylUc4+4yxt6 6BsiEzma6Ah5jexChYIwaB5Oi21yjc6bBb4l6z01WWJQ052OGaOBzi+tS5iGmc5DWH4/pFqX OIkgJVVgjPv2y41qV66QJJEi2wT4WUKLY1zA9s6KXbt8dVSzJsNFvsrAoFdtzc8v6uqCo0/W f0Id8MBKoqN5FniTHWNxYX6b2dFwq8i5Rh6Oxc6q75Kg8279+co3/tLCkU6pGga28K7tUP2z h9AUWENlnWJX/YhP8MLBZQQYAQoADwIbDAUCWgsSOgUJB9eShwAKCRCODp3rvH6PqtoND/41 ozCKAS4WWBBCU6AYLm2SoJ0EGhg1kIf9VMiqy5PKlSrAnW5yl4WJQcv5wER/7EzvZ49Gj8aG uRWfz3lyQU8dH2KG6KLilDFCZF0mViEo2C7O4QUx5xmbpMUq41fWjY947Xvd3QDisc1T1/7G uNBAALEZdqzwnKsT9G27e9Cd3AW3KsLAD4MhsALFARg6OuuwDCbLl6k5fu++26PEqORGtpJQ rRBWan9ZWb/Y57P126IVIylWiH6vt6iEPlaEHBU8H9+Z0WF6wJ5rNz9gR6GhZhmo1qsyNedD 1HzOsXQhvCinsErpZs99VdZSF3d54dac8ypH4hvbjSmXZjY3Sblhyc6RLYlru5UXJFh7Hy+E TMuCg3hIVbdyFSDkvxVlvhHgUSf8+Uk3Ya4MO4a5l9ElUqxpSqYH7CvuwkG+mH5mN8tK3CCd +aKPCxUFfil62DfTa7YgLovr7sHQB+VMQkNDPXleC+amNqJb423L8M2sfCi9gw/lA1ha6q80 ydgbcFEkNjqz4OtbrSwEHMy/ADsUWksYuzVbw7/pQTc6OAskESBr5igP7B/rIACUgiIjdOVB ktD1IQcezrDcuzVCIpuq8zC6LwLm7V1Tr6zfU9FWwnqzoQeQZH4QlP7MBuOeswCpxIl07mz9 jXz/74kjFsyRgZA+d6a1pGtOwITEBxtxxg== Message-ID: Date: Thu, 19 Jul 2018 13:41:15 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180718211013.14512-3-labbott@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Laura, Thanks again for your work. Please see some comments below. On 19.07.2018 00:10, Laura Abbott wrote: > Implementation of stackleak based heavily on the x86 version > > Signed-off-by: Laura Abbott > --- > Since last time: Minor style cleanups. Re-wrote check_alloca to > correctly handle all stack types. While doing that, I also realized > current_top_of_stack was incorrect so I fixed that as well. > --- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/processor.h | 17 ++++++++++++++ > arch/arm64/kernel/entry.S | 7 ++++++ > arch/arm64/kernel/process.c | 32 +++++++++++++++++++++++++++ > arch/arm64/kvm/hyp/Makefile | 3 ++- > drivers/firmware/efi/libstub/Makefile | 3 ++- > include/linux/stackleak.h | 1 + > 7 files changed, 62 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 42c090cf0292..216d36a49ab5 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -96,6 +96,7 @@ config ARM64 > select HAVE_ARCH_MMAP_RND_BITS > select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_SECCOMP_FILTER > + select HAVE_ARCH_STACKLEAK > select HAVE_ARCH_THREAD_STRUCT_WHITELIST > select HAVE_ARCH_TRACEHOOK > select HAVE_ARCH_TRANSPARENT_HUGEPAGE > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index a73ae1e49200..4f3062ee22c6 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -266,5 +266,22 @@ extern void __init minsigstksz_setup(void); > #define SVE_SET_VL(arg) sve_set_current_vl(arg) > #define SVE_GET_VL() sve_get_current_vl() > > +/* > + * For CONFIG_STACKLEAK Our config option is called CONFIG_GCC_PLUGIN_STACKLEAK. > + * > + * These need to be macros because otherwise we get stuck in a nightmare > + * of header definitions for the use of task_stack_page. > + */ > + > +#define current_top_of_stack() \ > +({ \ > + unsigned long _low = 0; \ > + unsigned long _high = 0; \ > + \ > + current_stack_type(current, current_stack_pointer, &_low, &_high); \ > + _high; \ > +}) Do you really need _low here? Ah, I see this in the previous patch: + if (stack_low && stack_high) { + *stack_low = low; + *stack_high = high; + } How about checking them against NULL separately? That would allow + current_stack_type(current, current_stack_pointer, NULL, &_high); Also a minor comment - how about aligning backslashes? > +#define on_thread_stack() (on_task_stack(current, current_stack_pointer, NULL, NULL)) > + > #endif /* __ASSEMBLY__ */ > #endif /* __ASM_PROCESSOR_H */ > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index 28ad8799406f..67d12016063d 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -431,6 +431,11 @@ tsk .req x28 // current thread_info > > .text > > + .macro stackleak_erase > +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK > + bl stackleak_erase > +#endif > + .endm > /* > * Exception vectors. > */ > @@ -910,6 +915,7 @@ ret_fast_syscall: > and x2, x1, #_TIF_WORK_MASK > cbnz x2, work_pending > enable_step_tsk x1, x2 > + stackleak_erase > kernel_exit 0 > ret_fast_syscall_trace: > enable_daif > @@ -936,6 +942,7 @@ ret_to_user: > cbnz x2, work_pending > finish_ret_to_user: > enable_step_tsk x1, x2 > + stackleak_erase > kernel_exit 0 > ENDPROC(ret_to_user) > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index e10bc363f533..904defa36689 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -493,3 +493,35 @@ void arch_setup_new_exec(void) > { > current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0; > } > + > +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK > +void __used stackleak_check_alloca(unsigned long size) > +{ > + unsigned long stack_left; > + enum stack_type type; > + unsigned long current_sp = current_stack_pointer; > + unsigned long low, high; > + > + type = current_stack_type(current, current_sp, &low, &high); > + BUG_ON(type == STACK_TYPE_UNKNOWN); > + > + stack_left = current_sp - low; > + > + if (size >= stack_left) { > + /* > + * Kernel stack depth overflow is detected, let's report that. > + * If CONFIG_VMAP_STACK is enabled, we can safely use BUG(). > + * If CONFIG_VMAP_STACK is disabled, BUG() handling can corrupt > + * the neighbour memory. CONFIG_SCHED_STACK_END_CHECK calls > + * panic() in a similar situation, so let's do the same if that > + * option is on. Otherwise just use BUG() and hope for the best. > + */ > +#if !defined(CONFIG_VMAP_STACK) && defined(CONFIG_SCHED_STACK_END_CHECK) > + panic("alloca() over the kernel stack boundary\n"); > +#else > + BUG(); > +#endif This comment and #if logic should be dropped, we should always use panic() here on arm64. Mark Rutland and I have worked out the solution for arm64 in this thread: http://openwall.com/lists/kernel-hardening/2018/05/11/12 Rationale: on arm64 with CONFIG_VMAP_STACK, a stack overflow results in panic() anyway. > + } > +} > +EXPORT_SYMBOL(stackleak_check_alloca); > +#endif > diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile > index 4313f7475333..2fabc2dc1966 100644 > --- a/arch/arm64/kvm/hyp/Makefile > +++ b/arch/arm64/kvm/hyp/Makefile > @@ -3,7 +3,8 @@ > # Makefile for Kernel-based Virtual Machine module, HYP part > # > > -ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING > +ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING \ > + $(DISABLE_STACKLEAK_PLUGIN) > > KVM=../../../../virt/kvm > > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile > index a34e9290a699..25dd2a14560d 100644 > --- a/drivers/firmware/efi/libstub/Makefile > +++ b/drivers/firmware/efi/libstub/Makefile > @@ -20,7 +20,8 @@ cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt > KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ > -D__NO_FORTIFY \ > $(call cc-option,-ffreestanding) \ > - $(call cc-option,-fno-stack-protector) > + $(call cc-option,-fno-stack-protector) \ > + $(DISABLE_STACKLEAK_PLUGIN) > > GCOV_PROFILE := n > KASAN_SANITIZE := n > diff --git a/include/linux/stackleak.h b/include/linux/stackleak.h > index b911b973d328..08420ec6b7c3 100644 > --- a/include/linux/stackleak.h > +++ b/include/linux/stackleak.h > @@ -5,6 +5,7 @@ > #include > #include > > +#include > /* > * Check that the poison value points to the unused hole in the > * virtual memory map for your platform. >