From patchwork Tue Jun 8 18:27:49 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 457541 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A980C47082 for ; Tue, 8 Jun 2021 19:17:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E84EC613B6 for ; Tue, 8 Jun 2021 19:17:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238087AbhFHTSy (ORCPT ); Tue, 8 Jun 2021 15:18:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:38704 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237135AbhFHTQx (ORCPT ); Tue, 8 Jun 2021 15:16:53 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9BD2D61476; Tue, 8 Jun 2021 18:51:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623178269; bh=4FxsOxl0IxUm91bhDt+hrgMMQPhGIbt4bIOedGfT3gk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QI0yRamoFrcdq1u3t/sO1CmFAV4QwfVS+LFIpjTK1VFCIlh+1obPi0dzvUeUvymeg GksqvorEYywHLik1LUF0H4/rB8YHfe0bcU/OdNzC6tcalxdAC5dPFNW9QwiYCc5P3J 7h2Fs0jPXeggKepsM+gdhrY8twf+3N/uhc1041fE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Christophe Leroy , "Naveen N. Rao" , Michael Ellerman Subject: [PATCH 5.12 139/161] powerpc/kprobes: Fix validation of prefixed instructions across page boundary Date: Tue, 8 Jun 2021 20:27:49 +0200 Message-Id: <20210608175950.145668740@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210608175945.476074951@linuxfoundation.org> References: <20210608175945.476074951@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Naveen N. Rao commit 82123a3d1d5a306fdf50c968a474cc60fe43a80f upstream. When checking if the probed instruction is the suffix of a prefixed instruction, we access the instruction at the previous word. If the probed instruction is the very first word of a module, we can end up trying to access an invalid page. Fix this by skipping the check for all instructions at the beginning of a page. Prefixed instructions cannot cross a 64-byte boundary and as such, we don't expect to encounter a suffix as the very first word in a page for kernel text. Even if there are prefixed instructions crossing a page boundary (from a module, for instance), the instruction will be illegal, so preventing probing on the suffix of such prefix instructions isn't worthwhile. Fixes: b4657f7650ba ("powerpc/kprobes: Don't allow breakpoints on suffixes") Cc: stable@vger.kernel.org # v5.8+ Reported-by: Christophe Leroy Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/0df9a032a05576a2fa8e97d1b769af2ff0eafbd6.1621416666.git.naveen.n.rao@linux.vnet.ibm.com Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/kprobes.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -108,7 +108,6 @@ int arch_prepare_kprobe(struct kprobe *p int ret = 0; struct kprobe *prev; struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr); - struct ppc_inst prefix = ppc_inst_read((struct ppc_inst *)(p->addr - 1)); if ((unsigned long)p->addr & 0x03) { printk("Attempt to register kprobe at an unaligned address\n"); @@ -116,7 +115,8 @@ int arch_prepare_kprobe(struct kprobe *p } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) { printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n"); ret = -EINVAL; - } else if (ppc_inst_prefixed(prefix)) { + } else if ((unsigned long)p->addr & ~PAGE_MASK && + ppc_inst_prefixed(ppc_inst_read((struct ppc_inst *)(p->addr - 1)))) { printk("Cannot register a kprobe on the second word of prefixed instruction\n"); ret = -EINVAL; }