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=-12.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 14D75C433DF for ; Fri, 21 Aug 2020 23:39:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E14D22072D for ; Fri, 21 Aug 2020 23:39:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=google.com header.i=@google.com header.b="tLmds5aw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726862AbgHUXjE (ORCPT ); Fri, 21 Aug 2020 19:39:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44788 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726740AbgHUXiy (ORCPT ); Fri, 21 Aug 2020 19:38:54 -0400 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 729F5C061575 for ; Fri, 21 Aug 2020 16:38:54 -0700 (PDT) Received: by mail-qv1-xf4a.google.com with SMTP id l18so2281400qvq.16 for ; Fri, 21 Aug 2020 16:38:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=wTTHOHLUpSJsOh9SXDMCY9S+w0wdFVpDu5cnszimX/A=; b=tLmds5awKD+FJoYN96kwnKij9GFM/pG0TOWm3XWwY7RIPcUjATUDrfyrJrQHJCIuzC 1XkCFnYfVOwG4ca9Ki81zRk1PhWizTWjfLzpUDIPranMwe2BF7S7EkBFFJOPFd4Fsowu mI5rukKBOLTTHJ4/nYEbTb880O4uHKMJEgSXs3YGPYNRJX05+3Nt942vNchy7zJ9wRCQ AHQPoZRCMKnAF7feD2eHbZyckVSJJNYAXEC1gJLDzthOagDsvKQweXy0SYabreDRZB8u RQfpslAk12zxgl0x4N4FK0656RUYGMeudH2TuA63k+nFdKUF0RsEKAtOhy/2bPsy54B1 N87A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=wTTHOHLUpSJsOh9SXDMCY9S+w0wdFVpDu5cnszimX/A=; b=MeuuDuoEq4ohz9+4FZX1LNv6QCoHrmRneK7BntdErf8oI2ucN+qWRf9tVy4DuwdfeS KuzZE+UrVAXi1ZzSRtG6zPn2s5YGPfpkVKqPSIsopS260hcSZrq8lX6b8VE4qkPisADM XmFAixdjuEhRBn7Pponats/B1RbxClFGtUly0GBjMvljKs8el30RBo/nbPW08hhDY1Vi CXVdIWXS8X7tclF0G82vgfsfIeN+PLfV9yu46V4JeyI/hnuLXWGD98Gp8iHGP1EE347k JuLUT86ifCfAzZa6gi8bIJbJej5mpmJufzkbvdthauxsSRwXRkVXDgI4pZKRyKj6a+ML l6SA== X-Gm-Message-State: AOAM531xNWOq41s2djTwl03dVAqmXk9YqBSQ1e4tMDbDPdGqyGAyxnkx mM7h4+uDqaiVUvM8tjqBaxKMpto2rtRvJ50= X-Google-Smtp-Source: ABdhPJy4/FIHmfbB1ei2uKSt3zT5fgTFGlHdwFHL+MIq3vrWnFAajV1NZ4y5+CZc6pq3XXE0PYqMN2s1gQsfAUc= X-Received: from ckennelly28.nyc.corp.google.com ([2620:0:1003:1003:3e52:82ff:fe5a:a91a]) (user=ckennelly job=sendgmr) by 2002:a05:6214:184b:: with SMTP id d11mr4672334qvy.21.1598053133560; Fri, 21 Aug 2020 16:38:53 -0700 (PDT) Date: Fri, 21 Aug 2020 19:38:47 -0400 In-Reply-To: <20200821233848.3904680-1-ckennelly@google.com> Message-Id: <20200821233848.3904680-2-ckennelly@google.com> Mime-Version: 1.0 References: <20200821233848.3904680-1-ckennelly@google.com> X-Mailer: git-send-email 2.28.0.297.g1956fa8f8d-goog Subject: [PATCH v4 1/2] fs/binfmt_elf: Use PT_LOAD p_align values for suitable start address. From: Chris Kennelly To: Alexander Viro , Alexey Dobriyan , Song Liu Cc: David Rientjes , Ian Rogers , Hugh Dickens , Andrew Morton , Suren Baghdasaryan , Sandeep Patil , Fangrui Song , Nick Desaulniers , clang-built-linux@googlegroups.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Kennelly Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The current ELF loading mechancism provides page-aligned mappings. This can lead to the program being loaded in a way unsuitable for file-backed, transparent huge pages when handling PIE executables. For binaries built with increased alignment, this limits the number of bits usable for ASLR, but provides some randomization over using fixed load addresses/non-PIE binaries. Tested: verified program with -Wl,-z,max-page-size=0x200000 loading Signed-off-by: Chris Kennelly --- fs/binfmt_elf.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 13d053982dd73..96370e3e36872 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -421,6 +422,26 @@ static int elf_read(struct file *file, void *buf, size_t len, loff_t pos) return 0; } +static unsigned long maximum_alignment(struct elf_phdr *cmds, int nr) +{ + unsigned long alignment = 0; + int i; + + for (i = 0; i < nr; i++) { + if (cmds[i].p_type == PT_LOAD) { + unsigned long p_align = cmds[i].p_align; + + /* skip non-power of two alignments as invalid */ + if (!is_power_of_2(p_align)) + continue; + alignment = max(alignment, p_align); + } + } + + /* ensure we align to at least one page */ + return ELF_PAGEALIGN(alignment); +} + /** * load_elf_phdrs() - load ELF program headers * @elf_ex: ELF header of the binary whose program headers should be loaded @@ -1008,6 +1029,7 @@ static int load_elf_binary(struct linux_binprm *bprm) int elf_prot, elf_flags; unsigned long k, vaddr; unsigned long total_size = 0; + unsigned long alignment; if (elf_ppnt->p_type != PT_LOAD) continue; @@ -1086,6 +1108,9 @@ static int load_elf_binary(struct linux_binprm *bprm) load_bias = ELF_ET_DYN_BASE; if (current->flags & PF_RANDOMIZE) load_bias += arch_mmap_rnd(); + alignment = maximum_alignment(elf_phdata, elf_ex->e_phnum); + if (alignment) + load_bias &= ~(alignment - 1); elf_flags |= MAP_FIXED; } else load_bias = 0; -- 2.28.0.297.g1956fa8f8d-goog