From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yu-cheng Yu Subject: [RFC PATCH 3/3] Prevent user from writing to IBT bitmap. Date: Fri, 28 Jun 2019 12:41:58 -0700 Message-ID: <20190628194158.2431-3-yu-cheng.yu@intel.com> References: <20190628194158.2431-1-yu-cheng.yu@intel.com> Return-path: In-Reply-To: <20190628194158.2431-1-yu-cheng.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org 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 , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit Cc: Yu-cheng Yu List-Id: linux-api@vger.kernel.org The IBT bitmap is visiable from user-mode, but not writable. Signed-off-by: Yu-cheng Yu --- arch/x86/mm/fault.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 59f4f66e4f2e..231196abb62e 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1454,6 +1454,13 @@ void do_user_addr_fault(struct pt_regs *regs, * we can handle it.. */ good_area: +#define USER_MODE_WRITE (FAULT_FLAG_WRITE | FAULT_FLAG_USER) + if (((flags & USER_MODE_WRITE) == USER_MODE_WRITE) && + (vma->vm_flags & VM_IBT)) { + bad_area_access_error(regs, hw_error_code, address, vma); + return; + } + if (unlikely(access_error(hw_error_code, vma))) { bad_area_access_error(regs, hw_error_code, address, vma); return; -- 2.17.1