Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752086AbaJQFtQ (ORCPT ); Fri, 17 Oct 2014 01:49:16 -0400 Received: from mail-ob0-f173.google.com ([209.85.214.173]:45713 "EHLO mail-ob0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750729AbaJQFtP (ORCPT ); Fri, 17 Oct 2014 01:49:15 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Fri, 17 Oct 2014 13:49:14 +0800 Message-ID: Subject: Re: From: Hillf Danton To: Kees Cook Cc: "hillf.zj" , LKML , Will Deacon , Rabin Vincent , Laura Abbott Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey Kees > From: Kees Cook > To: linux-kernel@vger.kernel.org > Cc: Kees Cook , Will Deacon , > Rabin Vincent , Laura Abbott , Rob > Herring , Leif Lindholm , Mark > Salter , Liu hua < > Subject: [PATCH v6 8/8] ARM: mm: allow text and rodata sections to be > read-only > Date: Thu, 18 Sep 2014 12:19:09 -0700 > Message-Id: <1411067949-10913-9-git-send-email-keescook@chromium.org> > X-Mailer: git-send-email 1.9.1 > In-Reply-To: <1411067949-10913-1-git-send-email-keescook@chromium.org> > References: <1411067949-10913-1-git-send-email-keescook@chromium.org> > X-MIMEDefang-Filter: outflux$Revision: 1.316 $ > X-HELO: www.outflux.net > X-Scanned-By: MIMEDefang 2.73 > Sender: linux-kernel-owner@vger.kernel.org > Precedence: bulk > List-Id: > X-Mailing-List: linux-kernel@vger.kernel.org > X-OriginalArrivalTime: 18 Sep 2014 19:23:14.0905 (UTC) > FILETIME=[FE5B1490:01CFD375] > X-RcptDomain: telfort.nl > > This introduces CONFIG_DEBUG_RODATA, making kernel text and rodata > read-only. Additionally, this splits rodata from text so that rodata can > also be NX, which may lead to wasted memory when aligning to SECTION_SIZE. > The read-only areas are made writable during ftrace updates and kexec. > > Signed-off-by: Kees Cook > Tested-by: Laura Abbott > Acked-by: Nicolas Pitre > --- > arch/arm/include/asm/cacheflush.h | 10 ++++++++ > arch/arm/kernel/ftrace.c | 19 ++++++++++++++++ > arch/arm/kernel/machine_kexec.c | 1 + > arch/arm/kernel/vmlinux.lds.S | 3 +++ > arch/arm/mm/Kconfig | 12 ++++++++++ > arch/arm/mm/init.c | 48 > ++++++++++++++++++++++++++++++++++++++- > 6 files changed, 92 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/cacheflush.h > b/arch/arm/include/asm/cacheflush.h > index 79ecb4f34ffb..9108292edcb5 100644 > --- a/arch/arm/include/asm/cacheflush.h > +++ b/arch/arm/include/asm/cacheflush.h > @@ -486,6 +486,16 @@ int set_memory_rw(unsigned long addr, int numpages); > int set_memory_x(unsigned long addr, int numpages); > int set_memory_nx(unsigned long addr, int numpages); > > +#ifdef CONFIG_DEBUG_RODATA > +void mark_rodata_ro(void); > +void set_kernel_text_rw(void); > +void set_kernel_text_ro(void); > +#else > +static inline void set_kernel_text_rw(void) { } > +static inline void set_kernel_text_ro(void) { } > +#endif > + > void flush_uprobe_xol_access(struct page *page, unsigned long uaddr, > void *kaddr, unsigned long len); > + > #endif > diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c > index af9a8a927a4e..b8c75e45a950 100644 > --- a/arch/arm/kernel/ftrace.c > +++ b/arch/arm/kernel/ftrace.c > @@ -15,6 +15,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -35,6 +36,22 @@ > > #define OLD_NOP 0xe1a00000 /* mov r0, r0 */ > > +static int __ftrace_modify_code(void *data) > +{ > + int *command = data; > + > + set_kernel_text_rw(); > + ftrace_modify_all_code(*command); > + set_kernel_text_ro(); > + > + return 0; > +} > + > +void arch_ftrace_update_code(int command) > +{ > + stop_machine(__ftrace_modify_code, &command, NULL); > +} > + > static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) > { > return rec->arch.old_mcount ? OLD_NOP : NOP; > @@ -73,6 +90,8 @@ int ftrace_arch_code_modify_prepare(void) > int ftrace_arch_code_modify_post_process(void) > { > set_all_modules_text_ro(); > + /* Make sure any TLB misses during machine stop are cleared. */ > + flush_tlb_all(); > return 0; > } > > diff --git a/arch/arm/kernel/machine_kexec.c > b/arch/arm/kernel/machine_kexec.c > index 8f75250cbe30..4423a565ef6f 100644 > --- a/arch/arm/kernel/machine_kexec.c > +++ b/arch/arm/kernel/machine_kexec.c > @@ -164,6 +164,7 @@ void machine_kexec(struct kimage *image) > reboot_code_buffer = page_address(image->control_code_page); > > /* Prepare parameters for reboot_code_buffer*/ > + set_kernel_text_rw(); > kexec_start_address = image->start; > kexec_indirection_page = page_list; > kexec_mach_type = machine_arch_type; > diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S > index a3d07ca2bbb4..542e58919bd9 100644 > --- a/arch/arm/kernel/vmlinux.lds.S > +++ b/arch/arm/kernel/vmlinux.lds.S > @@ -120,6 +120,9 @@ SECTIONS > ARM_CPU_KEEP(PROC_INFO) > } > > +#ifdef CONFIG_DEBUG_RODATA > + . = ALIGN(1< +#endif > RO_DATA(PAGE_SIZE) > > . = ALIGN(4); > diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig > index 7a0756df91a2..c9cd9c5bf1e1 100644 > --- a/arch/arm/mm/Kconfig > +++ b/arch/arm/mm/Kconfig > @@ -1017,3 +1017,15 @@ config ARM_KERNMEM_PERMS > padded to section-size (1MiB) boundaries (because their permissions > are different and splitting the 1M pages into 4K ones causes TLB > performance problems), wasting memory. > + > +config DEBUG_RODATA > + bool "Make kernel text and rodata read-only" > + depends on ARM_KERNMEM_PERMS > + default y > + help > + If this is set, kernel text and rodata will be made read-only. This > + is to help catch accidental or malicious attempts to change the > + kernel's executable code. Additionally splits rodata from kernel > + text so it can be made explicitly non-executable. This creates > + another section-size padded region, so it can waste more memory > + space while gaining the read-only protections. > diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c > index e6bfe76b2f59..dc2db779cdf4 100644 > --- a/arch/arm/mm/init.c > +++ b/arch/arm/mm/init.c > @@ -622,9 +622,10 @@ struct section_perm { > unsigned long end; > pmdval_t mask; > pmdval_t prot; > + pmdval_t clear; > }; > > -struct section_perm nx_perms[] = { > +static struct section_perm nx_perms[] = { > /* Make pages tables, etc before _stext RW (set NX). */ > { > .start = PAGE_OFFSET, > @@ -639,8 +640,35 @@ struct section_perm nx_perms[] = { > .mask = ~PMD_SECT_XN, > .prot = PMD_SECT_XN, > }, > +#ifdef CONFIG_DEBUG_RODATA > + /* Make rodata NX (set RO in ro_perms below). */ > + { > + .start = (unsigned long)__start_rodata, > + .end = (unsigned long)__init_begin, > + .mask = ~PMD_SECT_XN, > + .prot = PMD_SECT_XN, > + }, > +#endif > }; > > +#ifdef CONFIG_DEBUG_RODATA > +static struct section_perm ro_perms[] = { > + /* Make kernel code and rodata RX (set RO). */ > + { > + .start = (unsigned long)_stext, > + .end = (unsigned long)__init_begin, > +#ifdef CONFIG_ARM_LPAE > + .mask = ~PMD_SECT_RDONLY, > + .prot = PMD_SECT_RDONLY, > +#else > + .mask = ~(PMD_SECT_APX | PMD_SECT_AP_WRITE), > + .prot = PMD_SECT_APX | PMD_SECT_AP_WRITE, > + .clear = PMD_SECT_AP_WRITE, > +#endif > + }, > +}; > +#endif > + > /* > * Updates section permissions only for the current mm (sections are > * copied into each mm). During startup, this is the init_mm. Is only > @@ -704,6 +732,24 @@ static inline void fix_kernmem_perms(void) > { > set_section_perms(nx_perms, prot); > } > + > +#ifdef CONFIG_DEBUG_RODATA > +void mark_rodata_ro(void) > +{ > + set_section_perms(ro_perms, prot); > +} > + > +void set_kernel_text_rw(void) > +{ > + set_section_perms(ro_perms, clear); > +} > + > +void set_kernel_text_ro(void) > +{ > + set_section_perms(ro_perms, prot); > +} > +#endif /* CONFIG_DEBUG_RODATA */ > + > #else > static inline void fix_kernmem_perms(void) { } > #endif /* CONFIG_ARM_KERNMEM_PERMS */ > -- > 1.9.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/