From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54A6BC35DF5 for ; Tue, 25 Feb 2020 13:29:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C8E420658 for ; Tue, 25 Feb 2020 13:29:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729682AbgBYN27 (ORCPT ); Tue, 25 Feb 2020 08:28:59 -0500 Received: from foss.arm.com ([217.140.110.172]:50816 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725788AbgBYN27 (ORCPT ); Tue, 25 Feb 2020 08:28:59 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 429BFFEC; Tue, 25 Feb 2020 05:28:58 -0800 (PST) Received: from [10.162.16.116] (a075563-lin.blr.arm.com [10.162.16.116]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CE1763F703; Tue, 25 Feb 2020 05:28:49 -0800 (PST) Subject: Re: [PATCH v6 05/11] arm64: elf: Enable BTI at exec based on ELF program properties To: Mark Brown , Catalin Marinas , Will Deacon Cc: Alexander Viro , Paul Elliott , Peter Zijlstra , Yu-cheng Yu , Vincenzo Frascino , Marc Zyngier , Eugene Syromiatnikov , Szabolcs Nagy , "H . J . Lu" , Andrew Jones , Kees Cook , Arnd Bergmann , Jann Horn , Richard Henderson , =?UTF-8?Q?Kristina_Mart=c5=a1enko?= , Thomas Gleixner , Florian Weimer , Sudakshina Das , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, Dave Martin References: <20200212192906.53366-1-broonie@kernel.org> <20200212192906.53366-6-broonie@kernel.org> From: Amit Kachhap Message-ID: <275b9cdb-7835-0dfe-9bea-acb0d8301e36@arm.com> Date: Tue, 25 Feb 2020 18:58:50 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20200212192906.53366-6-broonie@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 2/13/20 12:59 AM, Mark Brown wrote: > From: Dave Martin > > For BTI protection to be as comprehensive as possible, it is > desirable to have BTI enabled from process startup. If this is not > done, the process must use mprotect() to enable BTI for each of its > executable mappings, but this is painful to do in the libc startup > code. It's simpler and more sound to have the kernel do it > instead. > > To this end, detect BTI support in the executable (or ELF > interpreter, as appropriate), via the > NT_GNU_PROGRAM_PROPERTY_TYPE_0 note, and tweak the initial prot > flags for the process' executable pages to include PROT_BTI as > appropriate. > > Signed-off-by: Dave Martin > Signed-off-by: Mark Brown > --- > arch/arm64/Kconfig | 3 +++ > arch/arm64/include/asm/elf.h | 50 ++++++++++++++++++++++++++++++++++++ > arch/arm64/kernel/process.c | 19 ++++++++++++++ > include/linux/elf.h | 6 ++++- > include/uapi/linux/elf.h | 6 +++++ > 5 files changed, 83 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index e37f4f07b990..d65d226a77ec 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -9,6 +9,7 @@ config ARM64 > select ACPI_MCFG if (ACPI && PCI) > select ACPI_SPCR_TABLE if ACPI > select ACPI_PPTT if ACPI > + select ARCH_BINFMT_ELF_STATE > select ARCH_CLOCKSOURCE_DATA > select ARCH_HAS_DEBUG_VIRTUAL > select ARCH_HAS_DEVMEM_IS_ALLOWED > @@ -33,6 +34,7 @@ config ARM64 > select ARCH_HAS_SYSCALL_WRAPPER > select ARCH_HAS_TEARDOWN_DMA_OPS if IOMMU_SUPPORT > select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST > + select ARCH_HAVE_ELF_PROT > select ARCH_HAVE_NMI_SAFE_CMPXCHG > select ARCH_INLINE_READ_LOCK if !PREEMPTION > select ARCH_INLINE_READ_LOCK_BH if !PREEMPTION > @@ -62,6 +64,7 @@ config ARM64 > select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION > select ARCH_KEEP_MEMBLOCK > select ARCH_USE_CMPXCHG_LOCKREF > + select ARCH_USE_GNU_PROPERTY if BINFMT_ELF > select ARCH_USE_QUEUED_RWLOCKS > select ARCH_USE_QUEUED_SPINLOCKS > select ARCH_SUPPORTS_MEMORY_FAILURE > diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h > index b618017205a3..fca3a48e9db5 100644 > --- a/arch/arm64/include/asm/elf.h > +++ b/arch/arm64/include/asm/elf.h > @@ -114,7 +114,11 @@ > > #ifndef __ASSEMBLY__ > > +#include > #include > +#include > +#include > +#include > #include /* for signal_minsigstksz, used by ARCH_DLINFO */ > > typedef unsigned long elf_greg_t; > @@ -224,6 +228,52 @@ extern int aarch32_setup_additional_pages(struct linux_binprm *bprm, > > #endif /* CONFIG_COMPAT */ > > +struct arch_elf_state { > + int flags; > +}; > + > +#define ARM64_ELF_BTI (1 << 0) > + > +#define INIT_ARCH_ELF_STATE { \ > + .flags = 0, \ > +} > + > +static inline int arch_parse_elf_property(u32 type, const void *data, > + size_t datasz, bool compat, > + struct arch_elf_state *arch) > +{ Does this check here make sense to skip running extra code? if (!system_supports_bti()) return 0; Although this check is there in arch_validate_prot. > + /* No known properties for AArch32 yet */ > + if (IS_ENABLED(CONFIG_COMPAT) && compat) > + return 0; > + > + if (type == GNU_PROPERTY_AARCH64_FEATURE_1_AND) { > + const u32 *p = data; > + > + if (datasz != sizeof(*p)) > + return -ENOEXEC; > + > + if (IS_ENABLED(CONFIG_ARM64_BTI) && > + (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) > + arch->flags |= ARM64_ELF_BTI; > + } > + > + return 0; > +} > + > +static inline int arch_elf_pt_proc(void *ehdr, void *phdr, > + struct file *f, bool is_interp, > + struct arch_elf_state *state) > +{ > + return 0; > +} > + > +static inline int arch_check_elf(void *ehdr, bool has_interp, > + void *interp_ehdr, > + struct arch_elf_state *state) > +{ > + return 0; > +} > + > #endif /* !__ASSEMBLY__ */ > > #endif > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index bbb0f0c145f6..7545a3f743c4 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -11,6 +11,7 @@ > > #include > #include > +#include > #include > #include > #include > @@ -18,6 +19,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -649,3 +651,20 @@ asmlinkage void __sched arm64_preempt_schedule_irq(void) > if (system_capabilities_finalized()) > preempt_schedule_irq(); > } > + > +#ifdef CONFIG_BINFMT_ELF > +int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, > + bool has_interp, bool is_interp) > +{ > + if (is_interp != has_interp) > + return prot; > + > + if (!(state->flags & ARM64_ELF_BTI)) > + return prot; > + > + if (prot & PROT_EXEC) > + prot |= PROT_BTI; > + > + return prot; > +} > +#endif > diff --git a/include/linux/elf.h b/include/linux/elf.h > index 1b6e8955c597..5d5b0321da0b 100644 > --- a/include/linux/elf.h > +++ b/include/linux/elf.h > @@ -63,7 +63,11 @@ extern int elf_coredump_extra_notes_size(void); > extern int elf_coredump_extra_notes_write(struct coredump_params *cprm); > #endif > > -/* NT_GNU_PROPERTY_TYPE_0 header */ > +/* > + * NT_GNU_PROPERTY_TYPE_0 header: > + * Keep this internal until/unless there is an agreed UAPI definition. > + * pr_type values (GNU_PROPERTY_*) are public and defined in the UAPI header. > + */ > struct gnu_property { > u32 pr_type; > u32 pr_datasz; > diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h > index 20900f4496b7..c6dd0215482e 100644 > --- a/include/uapi/linux/elf.h > +++ b/include/uapi/linux/elf.h > @@ -448,4 +448,10 @@ typedef struct elf64_note { > Elf64_Word n_type; /* Content type */ > } Elf64_Nhdr; > > +/* .note.gnu.property types for EM_AARCH64: */ > +#define GNU_PROPERTY_AARCH64_FEATURE_1_AND 0xc0000000 > + > +/* Bits for GNU_PROPERTY_AARCH64_FEATURE_1_BTI */ > +#define GNU_PROPERTY_AARCH64_FEATURE_1_BTI (1U << 0) > + > #endif /* _UAPI_LINUX_ELF_H */ >