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=-7.9 required=3.0 tests=DATE_IN_PAST_06_12, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 28B59C43218 for ; Fri, 26 Apr 2019 07:32:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 046F52089E for ; Fri, 26 Apr 2019 07:32:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726569AbfDZHc2 (ORCPT ); Fri, 26 Apr 2019 03:32:28 -0400 Received: from ex13-edg-ou-002.vmware.com ([208.91.0.190]:29121 "EHLO EX13-EDG-OU-002.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726545AbfDZHc1 (ORCPT ); Fri, 26 Apr 2019 03:32:27 -0400 Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-002.vmware.com (10.113.208.156) with Microsoft SMTP Server id 15.0.1156.6; Fri, 26 Apr 2019 00:31:45 -0700 Received: from sc2-haas01-esx0118.eng.vmware.com (sc2-haas01-esx0118.eng.vmware.com [10.172.44.118]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id 32C2B4129A; Fri, 26 Apr 2019 00:31:46 -0700 (PDT) From: Nadav Amit To: Peter Zijlstra , Borislav Petkov , Andy Lutomirski , Ingo Molnar CC: , , , Thomas Gleixner , Nadav Amit , Dave Hansen , , , , , , , , , , , Rick Edgecombe , Nadav Amit , Daniel Borkmann , Alexei Starovoitov Subject: [PATCH v5 23/23] bpf: Fail bpf_probe_write_user() while mm is switched Date: Thu, 25 Apr 2019 17:11:43 -0700 Message-ID: <20190426001143.4983-24-namit@vmware.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190426001143.4983-1-namit@vmware.com> References: <20190426001143.4983-1-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (EX13-EDG-OU-002.vmware.com: namit@vmware.com does not designate permitted sender hosts) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: 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; -- 2.17.1