From patchwork Wed Feb 19 12:31:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 11391317 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 2DC281580 for ; Wed, 19 Feb 2020 12:32:08 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0802F21D56 for ; Wed, 19 Feb 2020 12:32:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="e44JVr9f" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0802F21D56 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=lHustwa71JSyNZkxT2LLYyq8704/q8P8aDGwrTx4eGY=; b=e44JVr9ftvgzIB oSDSJY4QILsWJRY7MXoNBU+3P6Fyexprpvp/VXwM1eyheePOmfTYBQ7Asn4QzJGoWklE9OVIp/uLO VIGR7inMeS4RFgtkr3Tj+15ALdCqFVrAZj94vO2nWRGl3jj/3RTB7J66AbWQV366GC3f/LYP2VHgV CZkZpYBbeH/zobmYPz8/fKu+EM9yF4ZSCAlXpxnxs/l/2uSAg6Uqd9n7EyM6nq8D0o0e97tzek/sR mxtlRLMqYZbXctscliN/r2tz7Wjd7UNKy6MMcKuREDH9XGhHlDADlJUWdFAs4gK1C7F1KK6SgSY3M spjGaTbuun5R/YIpDPMw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4OWN-0005Hl-KN; Wed, 19 Feb 2020 12:32:07 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4OWK-0005HJ-VN for linux-arm-kernel@lists.infradead.org; Wed, 19 Feb 2020 12:32:06 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 76CD831B; Wed, 19 Feb 2020 04:32:02 -0800 (PST) Received: from arrakis.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 269123F6CF; Wed, 19 Feb 2020 04:32:01 -0800 (PST) From: Catalin Marinas To: Will Deacon , linux-mm@kvack.org Subject: [PATCH v2] mm: Avoid creating virtual address aliases in brk()/mmap()/mremap() Date: Wed, 19 Feb 2020 12:31:56 +0000 Message-Id: <20200219123156.86952-1-catalin.marinas@arm.com> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200219_043205_098353_B6F8A7B8 X-CRM114-Status: GOOD ( 15.23 ) X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.4.3 on bombadil.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [217.140.110.172 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Florian Weimer , Szabolcs Nagy , Victor Stinner , Andrey Konovalov , Andrew Morton , Linus Torvalds , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Currently the arm64 kernel ignores the top address byte passed to brk(), mmap() and mremap(). When the user is not aware of the 56-bit address limit or relies on the kernel to return an error, untagging such pointers has the potential to create address aliases in user-space. Passing a tagged address to munmap(), madvise() is permitted since the tagged pointer is expected to be inside an existing mapping. The current behaviour breaks the existing glibc malloc() implementation which relies on brk() with an address beyond 56-bit to be rejected by the kernel. Remove untagging in the above functions by partially reverting commit ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk"). In addition, update the arm64 tagged-address-abi.rst document accordingly. Link: https://bugzilla.redhat.com/1797052 Fixes: ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk") Cc: # 5.4.x- Cc: Andrew Morton Cc: Florian Weimer Reported-by: Victor Stinner Acked-by: Will Deacon Acked-by: Andrey Konovalov Signed-off-by: Catalin Marinas Reviewed-by: Andrew Morton --- Changes in v2: - Added note to tagged-address-abi.rst that this behaviour changed in v5.6 and some older kernel may still have the old behaviour. - Updated the commit log to make it clearer we broke the user ABI, also adding link to the Red Hat bugzilla entry. v1 available here: http://lkml.kernel.org/r/20200218122310.72710-1-catalin.marinas@arm.com Documentation/arm64/tagged-address-abi.rst | 11 +++++++++-- mm/mmap.c | 4 ---- mm/mremap.c | 1 - 3 files changed, 9 insertions(+), 7 deletions(-) diff --git a/Documentation/arm64/tagged-address-abi.rst b/Documentation/arm64/tagged-address-abi.rst index d4a85d535bf9..f6289116893c 100644 --- a/Documentation/arm64/tagged-address-abi.rst +++ b/Documentation/arm64/tagged-address-abi.rst @@ -44,8 +44,15 @@ The AArch64 Tagged Address ABI has two stages of relaxation depending how the user addresses are used by the kernel: 1. User addresses not accessed by the kernel but used for address space - management (e.g. ``mmap()``, ``mprotect()``, ``madvise()``). The use - of valid tagged pointers in this context is always allowed. + management (e.g. ``mprotect()``, ``madvise()``). The use of valid + tagged pointers in this context is allowed with the exception of + ``brk()``, ``mmap()`` and the ``new_address`` argument to + ``mremap()`` as these have the potential of aliasing with existing + user addresses. + + NOTE: This behaviour changed in v5.6 and so some earlier kernels may + incorrectly accept valid tagged pointers for the ``brk()``, + ``mmap()`` and ``mremap()`` system calls. 2. User addresses accessed by the kernel (e.g. ``write()``). This ABI relaxation is disabled by default and the application thread needs to diff --git a/mm/mmap.c b/mm/mmap.c index 6756b8bb0033..d681a20eb4ea 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -195,8 +195,6 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) bool downgraded = false; LIST_HEAD(uf); - brk = untagged_addr(brk); - if (down_write_killable(&mm->mmap_sem)) return -EINTR; @@ -1557,8 +1555,6 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len, struct file *file = NULL; unsigned long retval; - addr = untagged_addr(addr); - if (!(flags & MAP_ANONYMOUS)) { audit_mmap_fd(fd, flags); file = fget(fd); diff --git a/mm/mremap.c b/mm/mremap.c index 122938dcec15..af363063ea23 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -607,7 +607,6 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, LIST_HEAD(uf_unmap); addr = untagged_addr(addr); - new_addr = untagged_addr(new_addr); if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) return ret;