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[192.55.52.93]) by mx.google.com with ESMTPS id o12-v6si32492543plg.114.2018.11.19.13.54.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Nov 2018 13:54:25 -0800 (PST) Received-SPF: pass (google.com: domain of yu-cheng.yu@intel.com designates 192.55.52.93 as permitted sender) client-ip=192.55.52.93; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yu-cheng.yu@intel.com designates 192.55.52.93 as permitted sender) smtp.mailfrom=yu-cheng.yu@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Nov 2018 13:54:24 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,254,1539673200"; d="scan'208";a="93319879" Received: from yyu32-desk1.sc.intel.com ([143.183.136.147]) by orsmga008.jf.intel.com with ESMTP; 19 Nov 2018 13:54:23 -0800 From: Yu-cheng Yu To: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue Cc: Yu-cheng Yu Subject: [RFC PATCH v6 14/26] x86/mm: Shadow stack page fault error checking Date: Mon, 19 Nov 2018 13:47:57 -0800 Message-Id: <20181119214809.6086-15-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181119214809.6086-1-yu-cheng.yu@intel.com> References: <20181119214809.6086-1-yu-cheng.yu@intel.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP If a page fault is triggered by a shadow stack access (e.g. call/ret) or shadow stack management instructions (e.g. wrussq), then bit[6] of the page fault error code is set. In access_error(), verify a shadow stack page fault is within a shadow stack memory area. It is always an error otherwise. For a valid shadow stack access, set FAULT_FLAG_WRITE to effect copy-on-write. Signed-off-by: Yu-cheng Yu --- arch/x86/include/asm/traps.h | 2 ++ arch/x86/mm/fault.c | 18 ++++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index 20841d301e93..50e8a670624a 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -157,6 +157,7 @@ enum { * bit 3 == 1: use of reserved bit detected * bit 4 == 1: fault was an instruction fetch * bit 5 == 1: protection keys block access + * bit 6 == 1: shadow stack access fault */ enum x86_pf_error_code { X86_PF_PROT = 1 << 0, @@ -165,5 +166,6 @@ enum x86_pf_error_code { X86_PF_RSVD = 1 << 3, X86_PF_INSTR = 1 << 4, X86_PF_PK = 1 << 5, + X86_PF_SHSTK = 1 << 6, }; #endif /* _ASM_X86_TRAPS_H */ diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 71d4b9d4d43f..c3368fed706c 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1117,6 +1117,17 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) (error_code & X86_PF_INSTR), foreign)) return 1; + /* + * Verify X86_PF_SHSTK is within a shadow stack VMA. + * It is always an error if there is a shadow stack + * fault outside a shadow stack VMA. + */ + if (error_code & X86_PF_SHSTK) { + if (!(vma->vm_flags & VM_SHSTK)) + return 1; + return 0; + } + if (error_code & X86_PF_WRITE) { /* write, present and write, not present: */ if (unlikely(!(vma->vm_flags & VM_WRITE))) @@ -1313,6 +1324,13 @@ void do_user_addr_fault(struct pt_regs *regs, perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); + /* + * If the fault is caused by a shadow stack access, + * i.e. CALL/RET/SAVEPREVSSP/RSTORSSP, then set + * FAULT_FLAG_WRITE to effect copy-on-write. + */ + if (sw_error_code & X86_PF_SHSTK) + flags |= FAULT_FLAG_WRITE; if (sw_error_code & X86_PF_WRITE) flags |= FAULT_FLAG_WRITE; if (sw_error_code & X86_PF_INSTR)