From: Kees Cook <keescook@chromium.org> To: Laura Abbott <labbott@redhat.com> Cc: Alexander Popov <alex.popov@linux.com>, Mark Rutland <mark.rutland@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Kernel Hardening <kernel-hardening@lists.openwall.com>, linux-arm-kernel <linux-arm-kernel@lists.infradead.org>, LKML <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 2/2] arm64: Clear the stack Date: Wed, 2 May 2018 16:37:58 -0700 [thread overview] Message-ID: <CAGXu5j+LP8Yq8R=FUUA1TX2gD5G5xaYNVkt56aezZ_GLpxn69g@mail.gmail.com> (raw) In-Reply-To: <4b7e94c1-79c9-0380-25c6-762762ed595f@redhat.com> On Wed, May 2, 2018 at 4:07 PM, Laura Abbott <labbott@redhat.com> wrote: > On 05/02/2018 02:31 PM, Kees Cook wrote: >> struct stackleak { >> #ifdef CONFIG_GCC_PLUGIN_STACKLEAK >> unsigned long lowest; >> #ifdef CONFIG_STACKLEAK_METRICS >> unsigned long prev_lowest; >> #endif >> #endif >> }; >> > > Is this well defined across all compilers if the plugin is off? > This seems to compile with gcc at least but 0 sized structs > make me a little uneasy. Yup! Or at least, there have been no problems with this and the seccomp struct, which is empty when !CONFIG_SECCOMP. >> This is the only difference between x86 and arm64 in this code. What >> do you think about implementing on_thread_stack() to match x86: >> >> if (on_thread_stack()) >> boundary = current_stack_pointer; >> else >> boundary = current_top_of_stack(); >> >> then we could make this common code too instead of having two copies in >> arch/? >> > > The issue isn't on_thread_stack, it's current_top_of_stack which isn't > defined on arm64. I agree it would be good if the code would be common > but I'm not sure how much we want to start trying to force APIs. Ah, gotcha. Well, I'd rather we had an #ifdef here that two copies of the code. ;) >>> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK >>> +void __used check_alloca(unsigned long size) >>> +{ >>> + unsigned long sp, stack_left; >>> + >>> + sp = current_stack_pointer; >>> + >>> + stack_left = sp & (THREAD_SIZE - 1); >>> + BUG_ON(stack_left < 256 || size >= stack_left - 256); >>> +} >>> +EXPORT_SYMBOL(check_alloca); >> >> >> This is pretty different from x86. Is this just an artifact of ORC, or >> something else? >> > > This was based on the earlier version of x86. I'll confess to > not seeing how the current x86 version ended up with get_stack_info > but I suspect it's either related to ORC unwinding or it's best > practice. Alexander, what was the history here? -Kees -- Kees Cook Pixel Security
WARNING: multiple messages have this Message-ID (diff)
From: keescook@chromium.org (Kees Cook) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 2/2] arm64: Clear the stack Date: Wed, 2 May 2018 16:37:58 -0700 [thread overview] Message-ID: <CAGXu5j+LP8Yq8R=FUUA1TX2gD5G5xaYNVkt56aezZ_GLpxn69g@mail.gmail.com> (raw) In-Reply-To: <4b7e94c1-79c9-0380-25c6-762762ed595f@redhat.com> On Wed, May 2, 2018 at 4:07 PM, Laura Abbott <labbott@redhat.com> wrote: > On 05/02/2018 02:31 PM, Kees Cook wrote: >> struct stackleak { >> #ifdef CONFIG_GCC_PLUGIN_STACKLEAK >> unsigned long lowest; >> #ifdef CONFIG_STACKLEAK_METRICS >> unsigned long prev_lowest; >> #endif >> #endif >> }; >> > > Is this well defined across all compilers if the plugin is off? > This seems to compile with gcc at least but 0 sized structs > make me a little uneasy. Yup! Or at least, there have been no problems with this and the seccomp struct, which is empty when !CONFIG_SECCOMP. >> This is the only difference between x86 and arm64 in this code. What >> do you think about implementing on_thread_stack() to match x86: >> >> if (on_thread_stack()) >> boundary = current_stack_pointer; >> else >> boundary = current_top_of_stack(); >> >> then we could make this common code too instead of having two copies in >> arch/? >> > > The issue isn't on_thread_stack, it's current_top_of_stack which isn't > defined on arm64. I agree it would be good if the code would be common > but I'm not sure how much we want to start trying to force APIs. Ah, gotcha. Well, I'd rather we had an #ifdef here that two copies of the code. ;) >>> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK >>> +void __used check_alloca(unsigned long size) >>> +{ >>> + unsigned long sp, stack_left; >>> + >>> + sp = current_stack_pointer; >>> + >>> + stack_left = sp & (THREAD_SIZE - 1); >>> + BUG_ON(stack_left < 256 || size >= stack_left - 256); >>> +} >>> +EXPORT_SYMBOL(check_alloca); >> >> >> This is pretty different from x86. Is this just an artifact of ORC, or >> something else? >> > > This was based on the earlier version of x86. I'll confess to > not seeing how the current x86 version ended up with get_stack_info > but I suspect it's either related to ORC unwinding or it's best > practice. Alexander, what was the history here? -Kees -- Kees Cook Pixel Security
next prev parent reply other threads:[~2018-05-02 23:38 UTC|newest] Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-06 14:22 [PATCH v11 0/6] Introduce the STACKLEAK feature and a test for it Alexander Popov 2018-04-06 14:22 ` [PATCH v11 1/6] gcc-plugins: Clean up the cgraph_create_edge* macros Alexander Popov 2018-04-06 14:22 ` [PATCH v11 2/6] x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls Alexander Popov 2018-04-16 18:29 ` Kees Cook 2018-04-18 18:33 ` Laura Abbott 2018-04-18 18:50 ` Dave Hansen 2018-04-24 1:03 ` Kees Cook 2018-04-24 4:23 ` Dave Hansen 2018-04-30 23:48 ` Kees Cook 2018-05-02 8:42 ` Thomas Gleixner 2018-05-02 12:38 ` Kees Cook 2018-05-02 12:39 ` Thomas Gleixner 2018-05-02 12:51 ` Kees Cook 2018-05-02 21:02 ` Kees Cook 2018-05-06 10:04 ` Thomas Gleixner 2018-04-06 14:22 ` [PATCH v11 3/6] gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack Alexander Popov 2018-04-06 14:22 ` [PATCH v11 4/6] lkdtm: Add a test for STACKLEAK Alexander Popov 2018-04-06 14:22 ` [PATCH v11 5/6] fs/proc: Show STACKLEAK metrics in the /proc file system Alexander Popov 2018-04-06 14:22 ` [PATCH v11 6/6] doc: self-protection: Add information about STACKLEAK feature Alexander Popov 2018-05-02 20:33 ` [PATCH 0/2] Stackleak for arm64 Laura Abbott 2018-05-02 20:33 ` Laura Abbott 2018-05-02 20:33 ` [PATCH 1/2] stackleak: Update " Laura Abbott 2018-05-02 20:33 ` Laura Abbott 2018-05-02 20:33 ` [PATCH 2/2] arm64: Clear the stack Laura Abbott 2018-05-02 20:33 ` Laura Abbott 2018-05-02 21:31 ` Kees Cook 2018-05-02 21:31 ` Kees Cook 2018-05-02 23:07 ` Laura Abbott 2018-05-02 23:07 ` Laura Abbott 2018-05-02 23:37 ` Kees Cook [this message] 2018-05-02 23:37 ` Kees Cook 2018-05-03 16:05 ` Alexander Popov 2018-05-03 16:05 ` Alexander Popov 2018-05-03 16:45 ` Kees Cook 2018-05-03 16:45 ` Kees Cook 2018-05-03 7:19 ` Mark Rutland 2018-05-03 7:19 ` Mark Rutland 2018-05-03 11:37 ` Ard Biesheuvel 2018-05-03 11:37 ` Ard Biesheuvel 2018-05-03 17:33 ` Alexander Popov 2018-05-03 17:33 ` Alexander Popov 2018-05-03 19:09 ` Laura Abbott 2018-05-03 19:09 ` Laura Abbott 2018-05-04 8:30 ` Alexander Popov 2018-05-04 8:30 ` Alexander Popov 2018-05-04 11:09 ` Mark Rutland 2018-05-04 11:09 ` Mark Rutland 2018-05-06 8:22 ` Alexander Popov 2018-05-06 8:22 ` Alexander Popov 2018-05-11 15:50 ` Alexander Popov 2018-05-11 15:50 ` Alexander Popov 2018-05-11 16:13 ` Mark Rutland 2018-05-11 16:13 ` Mark Rutland 2018-05-13 8:40 ` Alexander Popov 2018-05-13 8:40 ` Alexander Popov 2018-05-14 5:15 ` Mark Rutland 2018-05-14 5:15 ` Mark Rutland 2018-05-14 9:35 ` Alexander Popov 2018-05-14 9:35 ` Alexander Popov 2018-05-14 10:06 ` Mark Rutland 2018-05-14 10:06 ` Mark Rutland 2018-05-14 13:53 ` Alexander Popov 2018-05-14 13:53 ` Alexander Popov 2018-05-14 14:07 ` Mark Rutland 2018-05-14 14:07 ` Mark Rutland 2018-05-03 19:00 ` Laura Abbott 2018-05-03 19:00 ` Laura Abbott 2018-05-04 11:16 ` Mark Rutland 2018-05-04 11:16 ` Mark Rutland 2018-05-14 18:55 ` [PATCH v11 0/6] Introduce the STACKLEAK feature and a test for it Laura Abbott -- strict thread matches above, loose matches on Subject: below -- 2018-07-18 21:10 [PATCH 0/2] Stackleak for arm64 Laura Abbott 2018-07-18 21:10 ` [PATCH 2/2] arm64: Clear the stack Laura Abbott 2018-07-18 21:10 ` Laura Abbott 2018-07-19 2:20 ` Kees Cook 2018-07-19 2:20 ` Kees Cook 2018-07-19 10:41 ` Alexander Popov 2018-07-19 10:41 ` Alexander Popov 2018-07-19 11:41 ` Mark Rutland 2018-07-19 11:41 ` Mark Rutland 2018-02-21 1:13 [PATCH 0/2] Stackleak for arm64 Laura Abbott 2018-02-21 1:13 ` [PATCH 2/2] arm64: Clear the stack Laura Abbott 2018-02-21 1:13 ` Laura Abbott 2018-02-21 15:38 ` Mark Rutland 2018-02-21 15:38 ` Mark Rutland 2018-02-21 23:53 ` Laura Abbott 2018-02-21 23:53 ` Laura Abbott 2018-02-22 1:35 ` Laura Abbott 2018-02-22 1:35 ` Laura Abbott
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