From mboxrd@z Thu Jan 1 00:00:00 1970 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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 928C2C433F7 for ; Mon, 20 Jul 2020 16:18:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 720E020656 for ; Mon, 20 Jul 2020 16:18:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595261880; bh=oCqEXrTFfYzvCucMV7gFfqEy+cvS22N40zuJ4tPIm1I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fychtFT5Iz6aUH+hWRMbUslNXYsyPG6QsdN1ofL6U24dfuTqyQKflRw7TzGUL/jfJ 5y75XilSbfwM19sETmp5B76Y9hXbWYRmlMl5tglZpUE5UratsHoWx2iS8uSilJ7Q14 4Rut0RbjWBI5Vgr+JuDn2digHYd/0abfCw3WPzM0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388282AbgGTQOd (ORCPT ); Mon, 20 Jul 2020 12:14:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:54966 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388271AbgGTQOa (ORCPT ); Mon, 20 Jul 2020 12:14:30 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F285320684; Mon, 20 Jul 2020 16:14:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595261669; bh=oCqEXrTFfYzvCucMV7gFfqEy+cvS22N40zuJ4tPIm1I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2I9jtNlhYyv6FZUPlV43HD29UP0WL3ieIg5UM1193OilBbxbu+r2yPz6NyfZtdN/Y bHJ4DxiK2yBXowbGxxmsVMLCpxAbfSPZp6Y0IOSyqDshdq4lzSZZY4EUiX7V956SEK Nh5iX+QdSqmjUGaQcujxrVco4eQdSlaWXnls7CWo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sandipan Das , "Aneesh Kumar K.V" , Michael Ellerman Subject: [PATCH 5.7 199/244] powerpc/book3s64/pkeys: Fix pkey_access_permitted() for execute disable pkey Date: Mon, 20 Jul 2020 17:37:50 +0200 Message-Id: <20200720152835.310813986@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200720152825.863040590@linuxfoundation.org> References: <20200720152825.863040590@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Aneesh Kumar K.V commit 192b6a780598976feb7321ff007754f8511a4129 upstream. Even if the IAMR value denies execute access, the current code returns true from pkey_access_permitted() for an execute permission check, if the AMR read pkey bit is cleared. This results in repeated page fault loop with a test like below: #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #ifdef SYS_pkey_mprotect #undef SYS_pkey_mprotect #endif #ifdef SYS_pkey_alloc #undef SYS_pkey_alloc #endif #ifdef SYS_pkey_free #undef SYS_pkey_free #endif #undef PKEY_DISABLE_EXECUTE #define PKEY_DISABLE_EXECUTE 0x4 #define SYS_pkey_mprotect 386 #define SYS_pkey_alloc 384 #define SYS_pkey_free 385 #define PPC_INST_NOP 0x60000000 #define PPC_INST_BLR 0x4e800020 #define PROT_RWX (PROT_READ | PROT_WRITE | PROT_EXEC) static int sys_pkey_mprotect(void *addr, size_t len, int prot, int pkey) { return syscall(SYS_pkey_mprotect, addr, len, prot, pkey); } static int sys_pkey_alloc(unsigned long flags, unsigned long access_rights) { return syscall(SYS_pkey_alloc, flags, access_rights); } static int sys_pkey_free(int pkey) { return syscall(SYS_pkey_free, pkey); } static void do_execute(void *region) { /* jump to region */ asm volatile( "mtctr %0;" "bctrl" : : "r"(region) : "ctr", "lr"); } static void do_protect(void *region) { size_t pgsize; int i, pkey; pgsize = getpagesize(); pkey = sys_pkey_alloc(0, PKEY_DISABLE_EXECUTE); assert (pkey > 0); /* perform mprotect */ assert(!sys_pkey_mprotect(region, pgsize, PROT_RWX, pkey)); do_execute(region); /* free pkey */ assert(!sys_pkey_free(pkey)); } int main(int argc, char **argv) { size_t pgsize, numinsns; unsigned int *region; int i; /* allocate memory region to protect */ pgsize = getpagesize(); region = memalign(pgsize, pgsize); assert(region != NULL); assert(!mprotect(region, pgsize, PROT_RWX)); /* fill page with NOPs with a BLR at the end */ numinsns = pgsize / sizeof(region[0]); for (i = 0; i < numinsns - 1; i++) region[i] = PPC_INST_NOP; region[i] = PPC_INST_BLR; do_protect(region); return EXIT_SUCCESS; } The fix is to only check the IAMR for an execute check, the AMR value is not relevant. Fixes: f2407ef3ba22 ("powerpc: helper to validate key-access permissions of a pte") Cc: stable@vger.kernel.org # v4.16+ Reported-by: Sandipan Das Signed-off-by: Aneesh Kumar K.V [mpe: Add detail to change log, tweak wording & formatting] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200712132047.1038594-1-aneesh.kumar@linux.ibm.com Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/mm/book3s64/pkeys.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/arch/powerpc/mm/book3s64/pkeys.c +++ b/arch/powerpc/mm/book3s64/pkeys.c @@ -357,12 +357,14 @@ static bool pkey_access_permitted(int pk return true; pkey_shift = pkeyshift(pkey); - if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift))) - return true; + if (execute) + return !(read_iamr() & (IAMR_EX_BIT << pkey_shift)); + + amr = read_amr(); + if (write) + return !(amr & (AMR_WR_BIT << pkey_shift)); - amr = read_amr(); /* Delay reading amr until absolutely needed */ - return ((!write && !(amr & (AMR_RD_BIT << pkey_shift))) || - (write && !(amr & (AMR_WR_BIT << pkey_shift)))); + return !(amr & (AMR_RD_BIT << pkey_shift)); } bool arch_pte_access_permitted(u64 pte, bool write, bool execute)