From patchwork Tue Aug 18 06:12:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jann Horn X-Patchwork-Id: 11720041 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8B8531392 for ; Tue, 18 Aug 2020 06:12:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6EE1D2075E for ; Tue, 18 Aug 2020 06:12:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="hvkd25vZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726620AbgHRGMx (ORCPT ); Tue, 18 Aug 2020 02:12:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726228AbgHRGMu (ORCPT ); Tue, 18 Aug 2020 02:12:50 -0400 Received: from mail-qt1-x849.google.com (mail-qt1-x849.google.com [IPv6:2607:f8b0:4864:20::849]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B6280C061389 for ; Mon, 17 Aug 2020 23:12:50 -0700 (PDT) Received: by mail-qt1-x849.google.com with SMTP id r24so13753383qtu.3 for ; Mon, 17 Aug 2020 23:12:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=fmtjrw2NiRGUWmA+xNP8VLGlgPN22hDvuJd6RREZ1Uk=; b=hvkd25vZfBDuvPo6q33UmkfPOceVCVVmb65CH18K1GUDLyKlQ15oUB6XrL0MtXnusD JA7S6ecr6aTA9/jpVWkI4nsjHMnxUEnuZub7SALSoC/PwiQRAi1vHP3dBwQWdN3Q8LGj u3aQMJNkdFjRXPJl5yoikLOsLuqNkQMNBrZy/33KVY2fKCnPudfJYWMr/GnzFc/7McLP HBQ6jRmZiu7NXkCofQeTIm0cirWJR66MLsOcNpcqlDli1/f9c1c257d0Psfg8wEyQdbC QCH7vc9Urt48UXscwfp4cSibk4sLYdpp5F+orh6o0aENePXWjMde353uftORuYZovKFn TlVg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=fmtjrw2NiRGUWmA+xNP8VLGlgPN22hDvuJd6RREZ1Uk=; b=VAUjkGpYU0KLKr9ecVef8Y6q0T6FkxIxF4F30xOiQPcRpJis/NqV8NZANV6KQTMadQ N37mxuMZJqX9g591KDJzv/pCAOKGCk9bBTvVgvbCOpKUOixw8f02jFH69aXSqsaQN7UM X/SFjXf2EBjhZiTXu50pLUGXQmQo6oGf/uBuDjnyNxFnsT1+YsuKKg2TV+O4XYugcuTd SMQVIWAsxyVMPuCNKvyiRoGFpzo8pFUOBDdZtXecG3KZi9ITxKMM03a2PZGMhGSGXMgG zEwmZ3t5xCH6hl28/RGI0grmgpsT+PirWg8fdgS+/H6URa2wt+1lWp86wjzM5CKe5bS3 WRsg== X-Gm-Message-State: AOAM532RdSVtgaodqCWceQl7XhyJMFejVF1uwlG4WlTs90qYRmauKLq9 UP4/jFZwPoIXF9x58QObfxBZU75G9A== X-Google-Smtp-Source: ABdhPJwO+ELc+8ooufEtScS6e9Hlf7aAhZms+rK0szynExIR0CufYA7M7iBCYg4m4ltCXb6qLigMMsz8rA== X-Received: by 2002:a0c:b681:: with SMTP id u1mr17324890qvd.189.1597731169792; Mon, 17 Aug 2020 23:12:49 -0700 (PDT) Date: Tue, 18 Aug 2020 08:12:35 +0200 In-Reply-To: <20200818061239.29091-1-jannh@google.com> Message-Id: <20200818061239.29091-2-jannh@google.com> Mime-Version: 1.0 References: <20200818061239.29091-1-jannh@google.com> X-Mailer: git-send-email 2.28.0.220.ged08abb693-goog Subject: [PATCH v3 1/5] binfmt_elf_fdpic: Stop using dump_emit() on user pointers on !MMU From: Jann Horn To: Andrew Morton Cc: Linus Torvalds , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Alexander Viro , "Eric W . Biederman" , Oleg Nesterov Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org dump_emit() is for kernel pointers, and VMAs describe userspace memory. Let's be tidy here and avoid accessing userspace pointers under KERNEL_DS, even if it probably doesn't matter much on !MMU systems - especially given that it looks like we can just use the same get_dump_page() as on MMU if we move it out of the CONFIG_MMU block. One small change we have to make in get_dump_page() is to use __get_user_pages_locked() instead of __get_user_pages(), since the latter doesn't exist on nommu. On mmu builds, __get_user_pages_locked() will just call __get_user_pages() for us. Signed-off-by: Jann Horn --- fs/binfmt_elf_fdpic.c | 8 ------ mm/gup.c | 57 +++++++++++++++++++++---------------------- 2 files changed, 28 insertions(+), 37 deletions(-) diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index 50f845702b92..a53f83830986 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -1529,14 +1529,11 @@ static bool elf_fdpic_dump_segments(struct coredump_params *cprm) struct vm_area_struct *vma; for (vma = current->mm->mmap; vma; vma = vma->vm_next) { -#ifdef CONFIG_MMU unsigned long addr; -#endif if (!maydump(vma, cprm->mm_flags)) continue; -#ifdef CONFIG_MMU for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) { bool res; @@ -1552,11 +1549,6 @@ static bool elf_fdpic_dump_segments(struct coredump_params *cprm) if (!res) return false; } -#else - if (!dump_emit(cprm, (void *) vma->vm_start, - vma->vm_end - vma->vm_start)) - return false; -#endif } return true; } diff --git a/mm/gup.c b/mm/gup.c index ae096ea7583f..92519e5a44b3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1495,35 +1495,6 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) mmap_read_unlock(mm); return ret; /* 0 or negative error code */ } - -/** - * get_dump_page() - pin user page in memory while writing it to core dump - * @addr: user address - * - * Returns struct page pointer of user page pinned for dump, - * to be freed afterwards by put_page(). - * - * Returns NULL on any kind of failure - a hole must then be inserted into - * the corefile, to preserve alignment with its headers; and also returns - * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - - * allowing a hole to be left in the corefile to save diskspace. - * - * Called without mmap_lock, but after all other threads have been killed. - */ -#ifdef CONFIG_ELF_CORE -struct page *get_dump_page(unsigned long addr) -{ - struct vm_area_struct *vma; - struct page *page; - - if (__get_user_pages(current->mm, addr, 1, - FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma, - NULL) < 1) - return NULL; - flush_cache_page(vma, addr, page_to_pfn(page)); - return page; -} -#endif /* CONFIG_ELF_CORE */ #else /* CONFIG_MMU */ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, unsigned long nr_pages, struct page **pages, @@ -1569,6 +1540,34 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, } #endif /* !CONFIG_MMU */ +/** + * get_dump_page() - pin user page in memory while writing it to core dump + * @addr: user address + * + * Returns struct page pointer of user page pinned for dump, + * to be freed afterwards by put_page(). + * + * Returns NULL on any kind of failure - a hole must then be inserted into + * the corefile, to preserve alignment with its headers; and also returns + * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - + * allowing a hole to be left in the corefile to save diskspace. + * + * Called without mmap_lock, but after all other threads have been killed. + */ +#ifdef CONFIG_ELF_CORE +struct page *get_dump_page(unsigned long addr) +{ + struct vm_area_struct *vma; + struct page *page; + + if (__get_user_pages_locked(current->mm, addr, 1, &page, &vma, NULL, + FOLL_FORCE | FOLL_DUMP | FOLL_GET) < 1) + return NULL; + flush_cache_page(vma, addr, page_to_pfn(page)); + return page; +} +#endif /* CONFIG_ELF_CORE */ + #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA) static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages) {