From patchwork Mon Apr 22 18:58:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Edgecombe, Rick P" X-Patchwork-Id: 10911411 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A72AB1708 for ; Mon, 22 Apr 2019 18:59:17 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9DA5528762 for ; Mon, 22 Apr 2019 18:59:17 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 90EC5287CE; Mon, 22 Apr 2019 18:59:17 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4080528762 for ; Mon, 22 Apr 2019 18:59:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728824AbfDVS7H (ORCPT ); Mon, 22 Apr 2019 14:59:07 -0400 Received: from mga11.intel.com ([192.55.52.93]:60353 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728773AbfDVS6s (ORCPT ); Mon, 22 Apr 2019 14:58:48 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Apr 2019 11:58:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,382,1549958400"; d="scan'208";a="136417185" Received: from linksys13920.jf.intel.com (HELO rpedgeco-DESK5.jf.intel.com) ([10.54.75.11]) by orsmga008.jf.intel.com with ESMTP; 22 Apr 2019 11:58:42 -0700 From: Rick Edgecombe To: Borislav Petkov , Andy Lutomirski , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, Thomas Gleixner , Nadav Amit , Dave Hansen , Peter Zijlstra , linux_dti@icloud.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, akpm@linux-foundation.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, will.deacon@arm.com, ard.biesheuvel@linaro.org, kristen@linux.intel.com, deneen.t.dock@intel.com, Nadav Amit , Daniel Borkmann , Alexei Starovoitov , Rick Edgecombe Subject: [PATCH v4 23/23] bpf: Fail bpf_probe_write_user() while mm is switched Date: Mon, 22 Apr 2019 11:58:05 -0700 Message-Id: <20190422185805.1169-24-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190422185805.1169-1-rick.p.edgecombe@intel.com> References: <20190422185805.1169-1-rick.p.edgecombe@intel.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Nadav Amit When using a temporary mm, bpf_probe_write_user() should not be able to write to user memory, since user memory addresses may be used to map kernel memory. Detect these cases and fail bpf_probe_write_user() in such cases. Cc: Daniel Borkmann Cc: Alexei Starovoitov Reported-by: Jann Horn Suggested-by: Jann Horn Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe --- kernel/trace/bpf_trace.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index d64c00afceb5..94b0e37d90ef 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -14,6 +14,8 @@ #include #include +#include + #include "trace_probe.h" #include "trace.h" @@ -163,6 +165,10 @@ BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src, * access_ok() should prevent writing to non-user memory, but in * some situations (nommu, temporary switch, etc) access_ok() does * not provide enough validation, hence the check on KERNEL_DS. + * + * nmi_uaccess_okay() ensures the probe is not run in an interim + * state, when the task or mm are switched. This is specifically + * required to prevent the use of temporary mm. */ if (unlikely(in_interrupt() || @@ -170,6 +176,8 @@ BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src, return -EPERM; if (unlikely(uaccess_kernel())) return -EPERM; + if (unlikely(!nmi_uaccess_okay())) + return -EPERM; if (!access_ok(unsafe_ptr, size)) return -EPERM;