Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932505AbbLNTGV (ORCPT ); Mon, 14 Dec 2015 14:06:21 -0500 Received: from mga04.intel.com ([192.55.52.120]:16378 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932449AbbLNTGR (ORCPT ); Mon, 14 Dec 2015 14:06:17 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,428,1444719600"; d="scan'208";a="707234996" Subject: [PATCH 20/32] x86, pkeys: differentiate instruction fetches To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, x86@kernel.org, Dave Hansen , dave.hansen@linux.intel.com From: Dave Hansen Date: Mon, 14 Dec 2015 11:06:16 -0800 References: <20151214190542.39C4886D@viggo.jf.intel.com> In-Reply-To: <20151214190542.39C4886D@viggo.jf.intel.com> Message-Id: <20151214190616.A3CB5832@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7591 Lines: 182 From: Dave Hansen As discussed earlier, we attempt to enforce protection keys in software. However, the code checks all faults to ensure that they are not violating protection key permissions. It was assumed that all faults are either write faults where we check PKRU[key].WD (write disable) or read faults where we check the AD (access disable) bit. But, there is a third category of faults for protection keys: instruction faults. Instruction faults never run afoul of protection keys because they do not affect instruction fetches. So, plumb the PF_INSTR bit down in to the arch_vma_access_permitted() function where we do the protection key checks. We also add a new FAULT_FLAG_INSTRUCTION. This is because handle_mm_fault() is not passed the architecture-specific error_code where we keep PF_INSTR, so we need to encode the instruction fetch information in to the arch-generic fault flags. Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner --- b/arch/powerpc/include/asm/mmu_context.h | 2 +- b/arch/s390/include/asm/mmu_context.h | 2 +- b/arch/x86/include/asm/mmu_context.h | 5 ++++- b/arch/x86/mm/fault.c | 8 ++++++-- b/include/asm-generic/mm_hooks.h | 2 +- b/include/linux/mm.h | 1 + b/mm/gup.c | 11 +++++++++-- b/mm/memory.c | 1 + 8 files changed, 24 insertions(+), 8 deletions(-) diff -puN arch/powerpc/include/asm/mmu_context.h~pkeys-16-allow-execute-on-unreadable arch/powerpc/include/asm/mmu_context.h --- a/arch/powerpc/include/asm/mmu_context.h~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.794026685 -0800 +++ b/arch/powerpc/include/asm/mmu_context.h 2015-12-14 10:42:47.809027357 -0800 @@ -149,7 +149,7 @@ static inline void arch_bprm_mm_init(str } static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, - bool write, bool foreign) + bool write, bool execute, bool foreign) { /* by default, allow everything */ return true; diff -puN arch/s390/include/asm/mmu_context.h~pkeys-16-allow-execute-on-unreadable arch/s390/include/asm/mmu_context.h --- a/arch/s390/include/asm/mmu_context.h~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.796026774 -0800 +++ b/arch/s390/include/asm/mmu_context.h 2015-12-14 10:42:47.809027357 -0800 @@ -131,7 +131,7 @@ static inline void arch_bprm_mm_init(str } static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, - bool write, bool foreign) + bool write, bool execute, bool foreign) { /* by default, allow everything */ return true; diff -puN arch/x86/include/asm/mmu_context.h~pkeys-16-allow-execute-on-unreadable arch/x86/include/asm/mmu_context.h --- a/arch/x86/include/asm/mmu_context.h~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.797026819 -0800 +++ b/arch/x86/include/asm/mmu_context.h 2015-12-14 10:42:47.809027357 -0800 @@ -291,8 +291,11 @@ static inline bool vma_is_foreign(struct } static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, - bool write, bool foreign) + bool write, bool execute, bool foreign) { + /* pkeys never affect instruction fetches */ + if (execute) + return true; /* allow access if the VMA is not one from this process */ if (foreign || vma_is_foreign(vma)) return true; diff -puN arch/x86/mm/fault.c~pkeys-16-allow-execute-on-unreadable arch/x86/mm/fault.c --- a/arch/x86/mm/fault.c~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.799026909 -0800 +++ b/arch/x86/mm/fault.c 2015-12-14 10:42:47.810027402 -0800 @@ -908,7 +908,8 @@ static inline bool bad_area_access_from_ if (error_code & PF_PK) return true; /* this checks permission keys on the VMA: */ - if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), foreign)) + if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), + (error_code & PF_INSTR), foreign)) return true; return false; } @@ -1112,7 +1113,8 @@ access_error(unsigned long error_code, s * faults just to hit a PF_PK as soon as we fill in a * page. */ - if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), foreign)) + if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), + (error_code & PF_INSTR), foreign)) return 1; if (error_code & PF_WRITE) { @@ -1267,6 +1269,8 @@ __do_page_fault(struct pt_regs *regs, un if (error_code & PF_WRITE) flags |= FAULT_FLAG_WRITE; + if (error_code & PF_INSTR) + flags |= FAULT_FLAG_INSTRUCTION; /* * When running in the kernel we expect faults to occur only to diff -puN include/asm-generic/mm_hooks.h~pkeys-16-allow-execute-on-unreadable include/asm-generic/mm_hooks.h --- a/include/asm-generic/mm_hooks.h~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.801026998 -0800 +++ b/include/asm-generic/mm_hooks.h 2015-12-14 10:42:47.810027402 -0800 @@ -27,7 +27,7 @@ static inline void arch_bprm_mm_init(str } static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, - bool write, bool foreign) + bool write, bool execute, bool foreign) { /* by default, allow everything */ return true; diff -puN include/linux/mm.h~pkeys-16-allow-execute-on-unreadable include/linux/mm.h --- a/include/linux/mm.h~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.802027043 -0800 +++ b/include/linux/mm.h 2015-12-14 10:42:47.811027447 -0800 @@ -238,6 +238,7 @@ extern pgprot_t protection_map[16]; #define FAULT_FLAG_TRIED 0x20 /* Second try */ #define FAULT_FLAG_USER 0x40 /* The fault originated in userspace */ #define FAULT_FLAG_FOREIGN 0x80 /* faulting for non current tsk/mm */ +#define FAULT_FLAG_INSTRUCTION 0x100 /* The fault was during an instruction fetch */ /* * vm_fault is filled by the the pagefault handler and passed to the vma's diff -puN mm/gup.c~pkeys-16-allow-execute-on-unreadable mm/gup.c --- a/mm/gup.c~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.804027133 -0800 +++ b/mm/gup.c 2015-12-14 10:42:47.812027491 -0800 @@ -396,7 +396,11 @@ static int check_vma_flags(struct vm_are if (!(vm_flags & VM_MAYREAD)) return -EFAULT; } - if (!arch_vma_access_permitted(vma, write, foreign)) + /* + * gups are always data accesses, not instruction + * fetches, so execute=false here + */ + if (!arch_vma_access_permitted(vma, write, false, foreign)) return -EFAULT; return 0; } @@ -576,8 +580,11 @@ bool vma_permits_fault(struct vm_area_st /* * The architecture might have a hardware protection * mechanism other than read/write that can deny access. + * + * gup always represents data access, not instruction + * fetches, so execute=false here: */ - if (!arch_vma_access_permitted(vma, write, foreign)) + if (!arch_vma_access_permitted(vma, write, false, foreign)) return false; return true; diff -puN mm/memory.c~pkeys-16-allow-execute-on-unreadable mm/memory.c --- a/mm/memory.c~pkeys-16-allow-execute-on-unreadable 2015-12-14 10:42:47.806027223 -0800 +++ b/mm/memory.c 2015-12-14 10:42:47.813027536 -0800 @@ -3346,6 +3346,7 @@ static int __handle_mm_fault(struct mm_s pte_t *pte; if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE, + flags & FAULT_FLAG_INSTRUCTION, flags & FAULT_FLAG_FOREIGN)) return VM_FAULT_SIGSEGV; _ -- 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/