From patchwork Tue Sep 13 07:10:05 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baoquan He X-Patchwork-Id: 9328433 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2A07F60839 for ; Tue, 13 Sep 2016 07:10:26 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1CE342918E for ; Tue, 13 Sep 2016 07:10:26 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 107AE29198; Tue, 13 Sep 2016 07:10:26 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 34C742918E for ; Tue, 13 Sep 2016 07:10:25 +0000 (UTC) Received: (qmail 22361 invoked by uid 550); 13 Sep 2016 07:10:23 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: kernel-hardening@lists.openwall.com Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 22340 invoked from network); 13 Sep 2016 07:10:22 -0000 From: Baoquan He To: tonli@redhat.com, kexec@lists.infradead.org Cc: Thomas Garnier , horms@verge.net.au, keescook@chromium.org, kernel-hardening@lists.openwall.com Date: Tue, 13 Sep 2016 15:10:05 +0800 Message-Id: <1473750605-5955-1-git-send-email-bhe@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Tue, 13 Sep 2016 07:10:11 +0000 (UTC) Subject: [kernel-hardening] [PATCH v1] kexec/arch/i386: Add support for KASLR memory randomization X-Virus-Scanned: ClamAV using ClamSMTP From: Thomas Garnier Multiple changes were made on KASLR (right now in linux-next). One of them is randomizing the virtual address of the physical mapping, vmalloc and vmemmap memory sections. It breaks kdump ability to read physical memory. This change identifies if KASLR memories randomization is used by checking if the page_offset_base variable exists. It search for the correct PAGE_OFFSET value by looking at the loaded memory section and find the lowest aligned on PUD (the randomization level). Related commits on linux-next: - 0483e1fa6e09d4948272680f691dccb1edb9677f: Base for randomization - 021182e52fe01c1f7b126f97fd6ba048dc4234fd: Enable for PAGE_OFFSET Signed-off-by: Thomas Garnier --- kexec/arch/i386/crashdump-x86.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c index bbc0f35..ab833d4 100644 --- a/kexec/arch/i386/crashdump-x86.c +++ b/kexec/arch/i386/crashdump-x86.c @@ -102,11 +102,10 @@ static int get_kernel_paddr(struct kexec_info *UNUSED(info), return -1; } -/* Retrieve kernel _stext symbol virtual address from /proc/kallsyms */ -static unsigned long long get_kernel_stext_sym(void) +/* Retrieve kernel symbol virtual address from /proc/kallsyms */ +static unsigned long long get_kernel_sym(const char *symbol) { const char *kallsyms = "/proc/kallsyms"; - const char *stext = "_stext"; char sym[128]; char line[128]; FILE *fp; @@ -122,13 +121,13 @@ static unsigned long long get_kernel_stext_sym(void) while(fgets(line, sizeof(line), fp) != NULL) { if (sscanf(line, "%Lx %c %s", &vaddr, &type, sym) != 3) continue; - if (strcmp(sym, stext) == 0) { - dbgprintf("kernel symbol %s vaddr = %16llx\n", stext, vaddr); + if (strcmp(sym, symbol) == 0) { + dbgprintf("kernel symbol %s vaddr = %16llx\n", symbol, vaddr); return vaddr; } } - fprintf(stderr, "Cannot get kernel %s symbol address\n", stext); + fprintf(stderr, "Cannot get kernel %s symbol address\n", symbol); return 0; } @@ -151,6 +150,8 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info), off_t size; uint32_t elf_flags = 0; uint64_t stext_sym; + const unsigned long long pud_mask = ~((1 << 30) - 1); + unsigned long long vaddr, lowest_vaddr = 0; if (elf_info->machine != EM_X86_64) return 0; @@ -180,9 +181,23 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info), end_phdr = &ehdr.e_phdr[ehdr.e_phnum]; + /* Search for the real PAGE_OFFSET when KASLR memory randomization + * is enabled */ + if (get_kernel_sym("page_offset_base") != 0) { + for(phdr = ehdr.e_phdr; phdr != end_phdr; phdr++) { + if (phdr->p_type == PT_LOAD) { + vaddr = phdr->p_vaddr & pud_mask; + if (lowest_vaddr == 0 || lowest_vaddr > vaddr) + lowest_vaddr = vaddr; + } + } + if (lowest_vaddr != 0) + elf_info->page_offset = lowest_vaddr; + } + /* Traverse through the Elf headers and find the region where * _stext symbol is located in. That's where kernel is mapped */ - stext_sym = get_kernel_stext_sym(); + stext_sym = get_kernel_sym("_stext"); for(phdr = ehdr.e_phdr; stext_sym && phdr != end_phdr; phdr++) { if (phdr->p_type == PT_LOAD) { unsigned long long saddr = phdr->p_vaddr;