From patchwork Fri Apr 3 21:21:29 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masami Hiramatsu X-Patchwork-Id: 16237 Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n33LLwZm010994 for ; Fri, 3 Apr 2009 21:21:58 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756339AbZDCVV5 (ORCPT ); Fri, 3 Apr 2009 17:21:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754125AbZDCVV5 (ORCPT ); Fri, 3 Apr 2009 17:21:57 -0400 Received: from mx2.redhat.com ([66.187.237.31]:50959 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753171AbZDCVV4 (ORCPT ); Fri, 3 Apr 2009 17:21:56 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n33LKVeU022935; Fri, 3 Apr 2009 17:20:31 -0400 Received: from ns3.rdu.redhat.com (ns3.rdu.redhat.com [10.11.255.199]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n33LK7h4028241; Fri, 3 Apr 2009 17:20:07 -0400 Received: from [10.16.2.46] (dhcp-100-2-46.bos.redhat.com [10.16.2.46]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id n33LK4Nf032264; Fri, 3 Apr 2009 17:20:05 -0400 Message-ID: <49D67DD9.2050008@redhat.com> Date: Fri, 03 Apr 2009 17:21:29 -0400 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Jim Keniston CC: ananth@in.ibm.com, Ingo Molnar , LKML , systemtap-ml , kvm@vger.kernel.org, Andi Kleen , Andrew Morton , Arnaldo Carvalho de Melo , Steven Rostedt , Frederic Weisbecker Subject: [PATCH -tip 4/6 V4.2] x86: kprobes checks safeness of insertion address. References: <49D4F4E9.2030809@redhat.com> <20090403051854.GA4846@in.ibm.com> <49D63327.8020009@redhat.com> <1238779686.3568.18.camel@dyn9047018139.beaverton.ibm.com> <49D66166.9040002@redhat.com> In-Reply-To: <49D66166.9040002@redhat.com> X-Enigmail-Version: 0.95.7 X-Scanned-By: MIMEDefang 2.58 on 172.16.27.26 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org x86: kprobes checks safeness of insertion address. From: Masami Hiramatsu Ensure safeness of inserting kprobes by checking whether the specified address is at the first byte of a instruction. This is done by decoding probed function from its head to the probe point. changes from v4.1: - update comments according to Jim's suggestion. - s/lookup_symbol_attrs/kallsyms_lookup/ in a comment. Signed-off-by: Masami Hiramatsu Cc: Ananth N Mavinakayanahalli Cc: Jim Keniston Cc: Ingo Molnar --- arch/x86/kernel/kprobes.c | 54 +++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 54 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index 7b5169d..3d5e85f 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -48,12 +48,14 @@ #include #include #include +#include #include #include #include #include #include +#include void jprobe_return_end(void); @@ -244,6 +246,56 @@ retry: } } +/* Recover the probed instruction at addr for further analysis. */ +static int recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr) +{ + struct kprobe *kp; + kp = get_kprobe((void *)addr); + if (!kp) + return -EINVAL; + + /* + * Don't use p->ainsn.insn, which could be modified -- e.g., + * by fix_riprel(). + */ + memcpy(buf, kp->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); + buf[0] = kp->opcode; + return 0; +} + +/* Dummy buffers for kallsyms_lookup */ +static char __dummy_buf[KSYM_NAME_LEN]; + +/* Check if paddr is at an instruction boundary */ +static int __kprobes can_probe(unsigned long paddr) +{ + int ret; + unsigned long addr, offset = 0; + struct insn insn; + kprobe_opcode_t buf[MAX_INSN_SIZE]; + + /* Lookup symbol including addr */ + if (!kallsyms_lookup(paddr, NULL, &offset, NULL, __dummy_buf)) + return 0; + + /* Decode instructions */ + addr = paddr - offset; + while (addr < paddr) { + insn_init_kernel(&insn, (void *)addr); + insn_get_opcode(&insn); + if (OPCODE1(&insn) == BREAKPOINT_INSTRUCTION) { + ret = recover_probed_instruction(buf, addr); + if (ret) + return 0; + insn_init_kernel(&insn, buf); + } + insn_get_length(&insn); + addr += insn.length; + } + + return (addr == paddr); +} + /* * Returns non-zero if opcode modifies the interrupt flag. */ @@ -359,6 +411,8 @@ static void __kprobes arch_copy_kprobe(struct kprobe *p) int __kprobes arch_prepare_kprobe(struct kprobe *p) { + if (!can_probe((unsigned long)p->addr)) + return -EILSEQ; /* insn: must be on special executable page on x86. */ p->ainsn.insn = get_insn_slot(); if (!p->ainsn.insn)