From patchwork Thu Aug 13 14:48:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Thi=C3=A9baud_Weksteen?= X-Patchwork-Id: 11712565 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 9172C1744 for ; Thu, 13 Aug 2020 14:49:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7899820781 for ; Thu, 13 Aug 2020 14:49:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="brQMO6gX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726106AbgHMOtZ (ORCPT ); Thu, 13 Aug 2020 10:49:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726427AbgHMOtW (ORCPT ); Thu, 13 Aug 2020 10:49:22 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ABA38C061383 for ; Thu, 13 Aug 2020 07:49:21 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id w17so6922736ybl.9 for ; Thu, 13 Aug 2020 07:49:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc :content-transfer-encoding; bh=SEalPAaL/L400EFRhNDiBFOTi7pT/2kjH95anJxxgxI=; b=brQMO6gXvTrV2iIjuWTZ0a0xYUjqCYajx8AKbapPdz63kQ6krMyNmy5nRKklvp5bCn w41xOH4gOa0rGhWRgSSPP+zInZZipzm3Xqq+DqPQ7S6/3oroY0FUngVjJ9aQmrLaagsy OHY51yBqks31Yed941hnElUusZA5AB/Bs4X3me0ZHTrw+Zo6PKgEUeZdpdsnmCI96tKx i+4R3An/1umtigsoxZ5Tzx/ZAkI1K5WmIIv/E0C8amv1gcjVbo+CtTn6ZZtyB07QTzEj R49z2EfrHfvj5x3mCe4nJ33AYh0SEeiuvFmbeoKRsSas+zIFsnrflu0c8vsesRZNb54c byWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc :content-transfer-encoding; bh=SEalPAaL/L400EFRhNDiBFOTi7pT/2kjH95anJxxgxI=; b=neDFAn55UVbIfjWKrVChdyoI25QtF6Y83BTS1UYSNDcqblc7pGtUPHtLo4ckSet9/M wNI41qahrE9bFPHyTPBED1Yh3b0klvg1nXGUidIiN566EjpgV0lnvJP4gl3MDYul5nhX bjXFYDOIzm6+3cD16/e2/mAht8M/DMi6vWK6SUbXmgNRQcvFFwjfSmm68cDJwa9Nm0Cq sqlpb2rnCwN3Xt8Y6clFVXEynSVFEYYLSEghkKQrXx/kA6IonHbUEom7kgKTE67uaTfy KoV5lkpgOWZXcKcOA1JfNDsm+wgAN6ulDkKSBGaEnLPaY9oh8OKn/Pi6RKshmiB3H42Z 1JXw== X-Gm-Message-State: AOAM5335R8rznbP8t7vVvDf0MPpxIuu/PzKlZ/Pxoc/pbiUaDFMEvJpI puFXe8UZ0cApaW9r43+Ul7ficwS92A== X-Google-Smtp-Source: ABdhPJzZtAT/LPYngsPA4jm9kXHeRMw5dGr+JkxZ1qFWnJ/D4JgdZUTLHH3l2MhXFU0U+oHTuGsdHjNawA== X-Received: by 2002:a25:8689:: with SMTP id z9mr7576775ybk.226.1597330160576; Thu, 13 Aug 2020 07:49:20 -0700 (PDT) Date: Thu, 13 Aug 2020 16:48:58 +0200 Message-Id: <20200813144914.737306-1-tweek@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.28.0.236.gb10cc79966-goog Subject: [PATCH v2 1/2] selinux: add tracepoint on denials From: " =?utf-8?q?Thi=C3=A9baud_Weksteen?= " To: Paul Moore Cc: Nick Kralevich , " =?utf-8?q?Thi=C3=A9baud_Weksteen?= " , Joel Fernandes , Peter Enderborg , Stephen Smalley , Eric Paris , Steven Rostedt , Ingo Molnar , Mauro Carvalho Chehab , "David S. Miller" , Rob Herring , Arnd Bergmann , linux-kernel@vger.kernel.org, selinux@vger.kernel.org Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org The audit data currently captures which process and which target is responsible for a denial. There is no data on where exactly in the process that call occurred. Debugging can be made easier by being able to reconstruct the unified kernel and userland stack traces [1]. Add a tracepoint on the SELinux denials which can then be used by userland (i.e. perf). Although this patch could manually be added by each OS developer to trouble shoot a denial, adding it to the kernel streamlines the developers workflow. It is possible to use perf for monitoring the event: # perf record -e avc:selinux_audited -g -a ^C # perf report -g [...] 6.40% 6.40% audited=800000 tclass=4 | __libc_start_main | |--4.60%--__GI___ioctl | entry_SYSCALL_64 | do_syscall_64 | __x64_sys_ioctl | ksys_ioctl | binder_ioctl | binder_set_nice | can_nice | capable | security_capable | cred_has_capability.isra.0 | slow_avc_audit | common_lsm_audit | avc_audit_post_callback | avc_audit_post_callback | It is also possible to use the ftrace interface: # echo 1 > /sys/kernel/debug/tracing/events/avc/selinux_audited/enable # cat /sys/kernel/debug/tracing/trace tracer: nop entries-in-buffer/entries-written: 1/1 #P:8 [...] dmesg-3624 [001] 13072.325358: selinux_denied: audited=800000 tclass=4 [1] https://source.android.com/devices/tech/debug/native_stack_dump Signed-off-by: Thiébaud Weksteen Suggested-by: Joel Fernandes Reviewed-by: Peter Enderborg --- v2 changes: - update changelog to include usage examples MAINTAINERS | 1 + include/trace/events/avc.h | 37 +++++++++++++++++++++++++++++++++++++ security/selinux/avc.c | 5 +++++ 3 files changed, 43 insertions(+) create mode 100644 include/trace/events/avc.h diff --git a/MAINTAINERS b/MAINTAINERS index c8e8232c65da..0efaea0e144c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -15426,6 +15426,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git F: Documentation/ABI/obsolete/sysfs-selinux-checkreqprot F: Documentation/ABI/obsolete/sysfs-selinux-disable F: Documentation/admin-guide/LSM/SELinux.rst +F: include/trace/events/avc.h F: include/uapi/linux/selinux_netlink.h F: scripts/selinux/ F: security/selinux/ diff --git a/include/trace/events/avc.h b/include/trace/events/avc.h new file mode 100644 index 000000000000..07c058a9bbcd --- /dev/null +++ b/include/trace/events/avc.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Author: Thiébaud Weksteen + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM avc + +#if !defined(_TRACE_SELINUX_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_SELINUX_H + +#include + +TRACE_EVENT(selinux_audited, + + TP_PROTO(struct selinux_audit_data *sad), + + TP_ARGS(sad), + + TP_STRUCT__entry( + __field(unsigned int, tclass) + __field(unsigned int, audited) + ), + + TP_fast_assign( + __entry->tclass = sad->tclass; + __entry->audited = sad->audited; + ), + + TP_printk("tclass=%u audited=%x", + __entry->tclass, + __entry->audited) +); + +#endif + +/* This part must be outside protection */ +#include diff --git a/security/selinux/avc.c b/security/selinux/avc.c index d18cb32a242a..b0a0af778b70 100644 --- a/security/selinux/avc.c +++ b/security/selinux/avc.c @@ -31,6 +31,9 @@ #include "avc_ss.h" #include "classmap.h" +#define CREATE_TRACE_POINTS +#include + #define AVC_CACHE_SLOTS 512 #define AVC_DEF_CACHE_THRESHOLD 512 #define AVC_CACHE_RECLAIM 16 @@ -706,6 +709,8 @@ static void avc_audit_post_callback(struct audit_buffer *ab, void *a) u32 scontext_len; int rc; + trace_selinux_audited(sad); + rc = security_sid_to_context(sad->state, sad->ssid, &scontext, &scontext_len); if (rc)