From: Sami Tolvanen <samitolvanen@google.com> To: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <ardb@kernel.org>, Kees Cook <keescook@chromium.org>, 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>, "Paul E. McKenney" <paulmck@kernel.org>, Christoph Hellwig <hch@infradead.org>, Peter Zijlstra <peterz@infradead.org>, Sedat Dilek <sedat.dilek@gmail.com>, Catalin Marinas <catalin.marinas@arm.com>, bpf <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>, clang-built-linux <clang-built-linux@googlegroups.com> Subject: Re: [PATCH v5 14/18] arm64: add __nocfi to functions that jump to a physical address Date: Tue, 6 Apr 2021 10:43:50 -0700 [thread overview] Message-ID: <CABCJKuchDg74Md_He1nKgXKUf=pVEmiaVr_yJXB_yX+tKNhByA@mail.gmail.com> (raw) In-Reply-To: <20210406115357.GE96480@C02TD0UTHF1T.local> On Tue, Apr 6, 2021 at 4:54 AM Mark Rutland <mark.rutland@arm.com> wrote: > > [adding Ard for EFI runtime services bits] > > On Thu, Apr 01, 2021 at 04:32:12PM -0700, Sami Tolvanen wrote: > > Disable CFI checking for functions that switch to linear mapping and > > make an indirect call to a physical address, since the compiler only > > understands virtual addresses and the CFI check for such indirect calls > > would always fail. > > What does physical vs virtual have to do with this? Does the address > actually matter, or is this just a general thing that when calling an > assembly function we won't have a trampoline that the caller expects? No, this is about the actual address. The compiler-generated runtime checks only know about EL1 virtual addresses, so if we switch to a different address space, all indirect calls will trip CFI. > I wonder if we need to do something with asmlinkage here, perhaps? > > I didn't spot anything in the seriues handling EFI runtime services > calls, and I strongly suspect we need to do something for those, unless > they're handled implicitly by something else. > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > --- > > arch/arm64/include/asm/mmu_context.h | 2 +- > > arch/arm64/kernel/cpu-reset.h | 8 ++++---- > > arch/arm64/kernel/cpufeature.c | 2 +- > > 3 files changed, 6 insertions(+), 6 deletions(-) > >https://www.cnbc.com/2021/04/06/donald-trump-save-america-pac-has-85-million-on-hand-ahead-of-midterms.html > > diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h > > index 386b96400a57..d3cef9133539 100644 > > --- a/arch/arm64/include/asm/mmu_context.h > > +++ b/arch/arm64/include/asm/mmu_context.h > > @@ -119,7 +119,7 @@ static inline void cpu_install_idmap(void) > > * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD, > > * avoiding the possibility of conflicting TLB entries being allocated. > > */ > > -static inline void cpu_replace_ttbr1(pgd_t *pgdp) > > +static inline void __nocfi cpu_replace_ttbr1(pgd_t *pgdp) > > Given these are inlines, what's the effect when these are inlined into a > function that would normally use CFI? Does CFI get supressed for the > whole function, or just the bit that got inlined? Just for the bit that gets inlined. > Is there an attribute that we could place on a function pointer to tell > the compiler to not check calls via that pointer? If that existed we'd > be able to scope this much more tightly. There isn't, but I do agree that this would be a useful feature. Sami
WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com> To: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <ardb@kernel.org>, Kees Cook <keescook@chromium.org>, 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>, "Paul E. McKenney" <paulmck@kernel.org>, Christoph Hellwig <hch@infradead.org>, Peter Zijlstra <peterz@infradead.org>, Sedat Dilek <sedat.dilek@gmail.com>, Catalin Marinas <catalin.marinas@arm.com>, bpf <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>, clang-built-linux <clang-built-linux@googlegroups.com> Subject: Re: [PATCH v5 14/18] arm64: add __nocfi to functions that jump to a physical address Date: Tue, 6 Apr 2021 10:43:50 -0700 [thread overview] Message-ID: <CABCJKuchDg74Md_He1nKgXKUf=pVEmiaVr_yJXB_yX+tKNhByA@mail.gmail.com> (raw) In-Reply-To: <20210406115357.GE96480@C02TD0UTHF1T.local> On Tue, Apr 6, 2021 at 4:54 AM Mark Rutland <mark.rutland@arm.com> wrote: > > [adding Ard for EFI runtime services bits] > > On Thu, Apr 01, 2021 at 04:32:12PM -0700, Sami Tolvanen wrote: > > Disable CFI checking for functions that switch to linear mapping and > > make an indirect call to a physical address, since the compiler only > > understands virtual addresses and the CFI check for such indirect calls > > would always fail. > > What does physical vs virtual have to do with this? Does the address > actually matter, or is this just a general thing that when calling an > assembly function we won't have a trampoline that the caller expects? No, this is about the actual address. The compiler-generated runtime checks only know about EL1 virtual addresses, so if we switch to a different address space, all indirect calls will trip CFI. > I wonder if we need to do something with asmlinkage here, perhaps? > > I didn't spot anything in the seriues handling EFI runtime services > calls, and I strongly suspect we need to do something for those, unless > they're handled implicitly by something else. > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > --- > > arch/arm64/include/asm/mmu_context.h | 2 +- > > arch/arm64/kernel/cpu-reset.h | 8 ++++---- > > arch/arm64/kernel/cpufeature.c | 2 +- > > 3 files changed, 6 insertions(+), 6 deletions(-) > >https://www.cnbc.com/2021/04/06/donald-trump-save-america-pac-has-85-million-on-hand-ahead-of-midterms.html > > diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h > > index 386b96400a57..d3cef9133539 100644 > > --- a/arch/arm64/include/asm/mmu_context.h > > +++ b/arch/arm64/include/asm/mmu_context.h > > @@ -119,7 +119,7 @@ static inline void cpu_install_idmap(void) > > * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD, > > * avoiding the possibility of conflicting TLB entries being allocated. > > */ > > -static inline void cpu_replace_ttbr1(pgd_t *pgdp) > > +static inline void __nocfi cpu_replace_ttbr1(pgd_t *pgdp) > > Given these are inlines, what's the effect when these are inlined into a > function that would normally use CFI? Does CFI get supressed for the > whole function, or just the bit that got inlined? Just for the bit that gets inlined. > Is there an attribute that we could place on a function pointer to tell > the compiler to not check calls via that pointer? If that existed we'd > be able to scope this much more tightly. There isn't, but I do agree that this would be a useful feature. 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:[~2021-04-06 17:44 UTC|newest] Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-01 23:31 [PATCH v5 00/18] Add support for Clang CFI Sami Tolvanen 2021-04-01 23:31 ` Sami Tolvanen 2021-04-01 23:31 ` [PATCH v5 01/18] add " Sami Tolvanen 2021-04-01 23:31 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 02/18] cfi: add __cficanonical Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 03/18] mm: add generic function_nocfi macro Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-02 6:37 ` Christoph Hellwig 2021-04-02 6:37 ` Christoph Hellwig 2021-04-06 11:27 ` Mark Rutland 2021-04-06 11:27 ` Mark Rutland 2021-04-01 23:32 ` [PATCH v5 04/18] module: ensure __cfi_check alignment Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 05/18] workqueue: use WARN_ON_FUNCTION_MISMATCH Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 06/18] kthread: " Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 07/18] kallsyms: strip ThinLTO hashes from static functions Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 08/18] bpf: disable CFI in dispatcher functions Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 09/18] treewide: Change list_sort to use const pointers Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 10/18] lkdtm: use function_nocfi Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 11/18] psci: use function_nocfi for cpu_resume Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-06 11:27 ` Mark Rutland 2021-04-06 11:27 ` Mark Rutland 2021-04-01 23:32 ` [PATCH v5 12/18] arm64: implement function_nocfi Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-06 11:36 ` Mark Rutland 2021-04-06 11:36 ` Mark Rutland 2021-04-06 17:02 ` Sami Tolvanen 2021-04-06 17:02 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 13/18] arm64: use function_nocfi with __pa_symbol Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-06 11:41 ` Mark Rutland 2021-04-06 11:41 ` Mark Rutland 2021-04-01 23:32 ` [PATCH v5 14/18] arm64: add __nocfi to functions that jump to a physical address Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-06 11:53 ` Mark Rutland 2021-04-06 11:53 ` Mark Rutland 2021-04-06 12:59 ` Ard Biesheuvel 2021-04-06 12:59 ` Ard Biesheuvel 2021-04-06 17:43 ` Sami Tolvanen [this message] 2021-04-06 17:43 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 15/18] arm64: add __nocfi to __apply_alternatives Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 16/18] arm64: ftrace: use function_nocfi for ftrace_call Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-06 11:58 ` Mark Rutland 2021-04-06 11:58 ` Mark Rutland 2021-04-01 23:32 ` [PATCH v5 17/18] KVM: arm64: Disable CFI for nVHE Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-01 23:32 ` [PATCH v5 18/18] arm64: allow CONFIG_CFI_CLANG to be selected Sami Tolvanen 2021-04-01 23:32 ` Sami Tolvanen 2021-04-02 19:58 ` [PATCH v5 00/18] Add support for Clang CFI Nathan Chancellor 2021-04-02 19:58 ` Nathan Chancellor
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