From: Sami Tolvanen <samitolvanen@google.com> To: Kees Cook <keescook@chromium.org> Cc: Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, Masahiro Yamada <masahiroy@kernel.org>, Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>, Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>, bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch <linux-arch@vger.kernel.org>, linux-arm-kernel <linux-arm-kernel@lists.infradead.org>, linux-kbuild <linux-kbuild@vger.kernel.org>, PCI <linux-pci@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 04/17] module: cfi: ensure __cfi_check alignment Date: Tue, 16 Mar 2021 13:03:45 -0700 [thread overview] Message-ID: <CABCJKucW8dwXzEK-NZEHyQzN1wu-sGOiOqXFfR=C-PHvsn1+Dg@mail.gmail.com> (raw) In-Reply-To: <202103111837.813997B4@keescook> On Thu, Mar 11, 2021 at 6:39 PM Kees Cook <keescook@chromium.org> wrote: > > On Thu, Mar 11, 2021 at 04:49:06PM -0800, Sami Tolvanen wrote: > > CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page > > aligned and at the beginning of the .text section. While Clang would > > normally align the function correctly, it fails to do so for modules > > with no executable code. > > > > This change ensures the correct __cfi_check() location and > > alignment. It also discards the .eh_frame section, which Clang can > > generate with certain sanitizers, such as CFI. > > > > Link: https://bugs.llvm.org/show_bug.cgi?id=46293 > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > --- > > scripts/module.lds.S | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/scripts/module.lds.S b/scripts/module.lds.S > > index 168cd27e6122..552ddb084f76 100644 > > --- a/scripts/module.lds.S > > +++ b/scripts/module.lds.S > > @@ -3,10 +3,13 @@ > > * Archs are free to supply their own linker scripts. ld will > > * combine them automatically. > > */ > > +#include <asm/page.h> > > + > > SECTIONS { > > /DISCARD/ : { > > *(.discard) > > *(.discard.*) > > + *(.eh_frame) > > } > > > > __ksymtab 0 : { *(SORT(___ksymtab+*)) } > > @@ -40,7 +43,16 @@ SECTIONS { > > *(.rodata..L*) > > } > > > > - .text : { *(.text .text.[0-9a-zA-Z_]*) } > > +#ifdef CONFIG_CFI_CLANG > > + /* > > + * With CFI_CLANG, ensure __cfi_check is at the beginning of the > > + * .text section, and that the section is aligned to page size. > > + */ > > + .text : ALIGN(PAGE_SIZE) { > > + *(.text.__cfi_check) > > + *(.text .text.[0-9a-zA-Z_]* .text..L.cfi*) > > + } > > +#endif > > Whoops, I think this reverts to the default .text declaration when > CONFIG_CFI_CLANG is unset. Oops, thanks for pointing this out. I'll fix it in v2. > I think the only thing that needs the ifdef is the ALIGN, yes? Perhaps > something like this? > > #ifdef CONFIG_CFI_CLANG > # define ALIGN_CFI ALIGN(PAGE_SIZE) > #else > # define ALIGN_CFI > #endif > > .text : ALIGN_CFI { > *(.text.__cfi_check) > *(.text .text.[0-9a-zA-Z_]* .text..L.cfi*) > } Agreed, that looks better. Sami
WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com> To: Kees Cook <keescook@chromium.org> Cc: Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, Masahiro Yamada <masahiroy@kernel.org>, Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>, Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>, bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch <linux-arch@vger.kernel.org>, linux-arm-kernel <linux-arm-kernel@lists.infradead.org>, linux-kbuild <linux-kbuild@vger.kernel.org>, PCI <linux-pci@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 04/17] module: cfi: ensure __cfi_check alignment Date: Tue, 16 Mar 2021 13:03:45 -0700 [thread overview] Message-ID: <CABCJKucW8dwXzEK-NZEHyQzN1wu-sGOiOqXFfR=C-PHvsn1+Dg@mail.gmail.com> (raw) In-Reply-To: <202103111837.813997B4@keescook> On Thu, Mar 11, 2021 at 6:39 PM Kees Cook <keescook@chromium.org> wrote: > > On Thu, Mar 11, 2021 at 04:49:06PM -0800, Sami Tolvanen wrote: > > CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page > > aligned and at the beginning of the .text section. While Clang would > > normally align the function correctly, it fails to do so for modules > > with no executable code. > > > > This change ensures the correct __cfi_check() location and > > alignment. It also discards the .eh_frame section, which Clang can > > generate with certain sanitizers, such as CFI. > > > > Link: https://bugs.llvm.org/show_bug.cgi?id=46293 > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > --- > > scripts/module.lds.S | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/scripts/module.lds.S b/scripts/module.lds.S > > index 168cd27e6122..552ddb084f76 100644 > > --- a/scripts/module.lds.S > > +++ b/scripts/module.lds.S > > @@ -3,10 +3,13 @@ > > * Archs are free to supply their own linker scripts. ld will > > * combine them automatically. > > */ > > +#include <asm/page.h> > > + > > SECTIONS { > > /DISCARD/ : { > > *(.discard) > > *(.discard.*) > > + *(.eh_frame) > > } > > > > __ksymtab 0 : { *(SORT(___ksymtab+*)) } > > @@ -40,7 +43,16 @@ SECTIONS { > > *(.rodata..L*) > > } > > > > - .text : { *(.text .text.[0-9a-zA-Z_]*) } > > +#ifdef CONFIG_CFI_CLANG > > + /* > > + * With CFI_CLANG, ensure __cfi_check is at the beginning of the > > + * .text section, and that the section is aligned to page size. > > + */ > > + .text : ALIGN(PAGE_SIZE) { > > + *(.text.__cfi_check) > > + *(.text .text.[0-9a-zA-Z_]* .text..L.cfi*) > > + } > > +#endif > > Whoops, I think this reverts to the default .text declaration when > CONFIG_CFI_CLANG is unset. Oops, thanks for pointing this out. I'll fix it in v2. > I think the only thing that needs the ifdef is the ALIGN, yes? Perhaps > something like this? > > #ifdef CONFIG_CFI_CLANG > # define ALIGN_CFI ALIGN(PAGE_SIZE) > #else > # define ALIGN_CFI > #endif > > .text : ALIGN_CFI { > *(.text.__cfi_check) > *(.text .text.[0-9a-zA-Z_]* .text..L.cfi*) > } Agreed, that looks better. Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-03-16 20:04 UTC|newest] Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-12 0:49 [PATCH 00/17] Add support for Clang CFI Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 0:49 ` [PATCH 01/17] add " Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:39 ` Kees Cook 2021-03-12 2:39 ` Kees Cook 2021-03-12 0:49 ` [PATCH 02/17] cfi: add __cficanonical Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:40 ` Kees Cook 2021-03-12 2:40 ` Kees Cook 2021-03-12 20:28 ` Bjorn Helgaas 2021-03-12 20:28 ` Bjorn Helgaas 2021-03-12 0:49 ` [PATCH 03/17] mm: add generic __va_function and __pa_function macros Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:40 ` Kees Cook 2021-03-12 2:40 ` Kees Cook 2021-03-12 0:49 ` [PATCH 04/17] module: cfi: ensure __cfi_check alignment Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:39 ` Kees Cook 2021-03-12 2:39 ` Kees Cook 2021-03-16 20:03 ` Sami Tolvanen [this message] 2021-03-16 20:03 ` Sami Tolvanen 2021-03-12 0:49 ` [PATCH 05/17] workqueue: cfi: disable callback pointer check with modules Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:43 ` Kees Cook 2021-03-12 2:43 ` Kees Cook 2021-03-12 0:49 ` [PATCH 06/17] kthread: " Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:43 ` Kees Cook 2021-03-12 2:43 ` Kees Cook 2021-03-12 6:13 ` Christoph Hellwig 2021-03-12 6:13 ` Christoph Hellwig 2021-03-17 16:05 ` Sami Tolvanen 2021-03-17 16:05 ` Sami Tolvanen 2021-03-12 0:49 ` [PATCH 07/17] kallsyms: cfi: strip hashes from static functions Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:45 ` Kees Cook 2021-03-12 2:45 ` Kees Cook 2021-03-16 20:33 ` Sami Tolvanen 2021-03-16 20:33 ` Sami Tolvanen 2021-03-12 0:49 ` [PATCH 08/17] bpf: disable CFI in dispatcher functions Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:45 ` Kees Cook 2021-03-12 2:45 ` Kees Cook 2021-03-12 0:49 ` [PATCH 09/17] lib/list_sort: fix function type mismatches Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:45 ` Kees Cook 2021-03-12 2:45 ` Kees Cook 2021-03-12 0:49 ` [PATCH 10/17] lkdtm: use __va_function Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:45 ` Kees Cook 2021-03-12 2:45 ` Kees Cook 2021-03-12 0:49 ` [PATCH 11/17] psci: use __pa_function for cpu_resume Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:45 ` Kees Cook 2021-03-12 2:45 ` Kees Cook 2021-03-12 0:49 ` [PATCH 12/17] arm64: implement __va_function Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:46 ` Kees Cook 2021-03-12 2:46 ` Kees Cook 2021-03-12 0:49 ` [PATCH 13/17] arm64: use __pa_function Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:46 ` Kees Cook 2021-03-12 2:46 ` Kees Cook 2021-03-12 0:49 ` [PATCH 14/17] arm64: add __nocfi to functions that jump to a physical address Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:47 ` Kees Cook 2021-03-12 2:47 ` Kees Cook 2021-03-12 0:49 ` [PATCH 15/17] arm64: add __nocfi to __apply_alternatives Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:50 ` Kees Cook 2021-03-12 2:50 ` Kees Cook 2021-03-12 0:49 ` [PATCH 16/17] KVM: arm64: Disable CFI for nVHE Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:50 ` Kees Cook 2021-03-12 2:50 ` Kees Cook 2021-03-12 0:49 ` [PATCH 17/17] arm64: allow CONFIG_CFI_CLANG to be selected Sami Tolvanen 2021-03-12 0:49 ` Sami Tolvanen 2021-03-12 2:51 ` Kees Cook 2021-03-12 2:51 ` Kees Cook 2021-03-16 20:44 ` Sami Tolvanen 2021-03-16 20:44 ` Sami Tolvanen 2021-03-16 23:02 ` Kees Cook 2021-03-16 23:02 ` Kees Cook
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