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[209.132.180.67]) by mx.google.com with ESMTP id g40si4913860edb.369.2019.11.08.09.42.08; Fri, 08 Nov 2019 09:42:33 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@paul-moore-com.20150623.gappssmtp.com header.s=20150623 header.b="QypV/fGw"; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729668AbfKHRlc (ORCPT + 99 others); Fri, 8 Nov 2019 12:41:32 -0500 Received: from mail-lj1-f195.google.com ([209.85.208.195]:40698 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727296AbfKHRlb (ORCPT ); Fri, 8 Nov 2019 12:41:31 -0500 Received: by mail-lj1-f195.google.com with SMTP id q2so7092526ljg.7 for ; Fri, 08 Nov 2019 09:41:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=paul-moore-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2QJNYK/K5bdE2+Gkhht7sK48ftHkXUxqx+uBQkHd5Ts=; b=QypV/fGwmulAvg9MruUmhTnYlDA5c5MJNSURS6J4En6OmXgJCg+YzoAsYTaRujB1z2 hP3WmSV5DjQioueVpPG3QmHbeJLut69f9I+1DQgPU/BD2+aGZ3ejRua7P1liI5dYyec1 VbTAEROuyB6wd7DALgpKJp9LL/KaJ9AMfqXycwbHkU2tANkyllLPDuAhNMhMqpaYReqf jnxNC1z4Yt9DaALjdUk7R96nLeV8nV9MqdftZRgTPy97YQp3GAW3PvqRpPilOY8+Kgbs IlHk8zyie1aSeWSxTd7bQdJ0hzRGPU1XmE2G6lwTktuXjEodiYlwA3s2YIRwBwdtJYVc SV0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2QJNYK/K5bdE2+Gkhht7sK48ftHkXUxqx+uBQkHd5Ts=; b=c/OeMDRL4qtmC+crwd8jwod71LoUppknU0dtu3Pu6Vew44MUjXf4Mnf1f4eS0onIRu eiNG/TQrm2fbEropxvkboKcoc90eIfZ3d5IxhQLSeFBlTUGyVS0dxF4WBanKKx2YdrB7 uYWHUtM0FFq7HmJbuCDZrEvwGJXD+Vzq4+3CY8t7+c1YpFz+yBmjakU/VHWNwdq25fuj 7ABoewpVXaEhlmtaUVWYQIWZOU5PUEG/Ivg5dS1qFla3bGVwSNl7wW+LuD9Ntt44FuOW nbULHnMYZecV4xrpLxS2svry1e46mLXr5r98W/Hyvqs5rf+3cTCG/rpCt5MbUf3dkrTe lX4w== X-Gm-Message-State: APjAAAWkbNmVAYxLluPnPuDUHY8mYbU09ZQ5tUODulYKaHvs2RMGYwSc jW/XNjPwadL6+zPTaeJjnwqivicGkMREktqiKlsr X-Received: by 2002:a2e:4703:: with SMTP id u3mr584888lja.126.1573234887049; Fri, 08 Nov 2019 09:41:27 -0800 (PST) MIME-Version: 1.0 References: <0850eaa785e2ff30c8c4818fd53e9544b34ed884.1568834524.git.rgb@redhat.com> <20191025192031.ul3yjy2q57vsvier@madcap2.tricolour.ca> In-Reply-To: <20191025192031.ul3yjy2q57vsvier@madcap2.tricolour.ca> From: Paul Moore Date: Fri, 8 Nov 2019 12:41:16 -0500 Message-ID: Subject: Re: [PATCH ghak90 V7 08/21] audit: add contid support for signalling the audit daemon To: Richard Guy Briggs Cc: containers@lists.linux-foundation.org, linux-api@vger.kernel.org, Linux-Audit Mailing List , linux-fsdevel@vger.kernel.org, LKML , netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, sgrubb@redhat.com, omosnace@redhat.com, dhowells@redhat.com, simo@redhat.com, Eric Paris , Serge Hallyn , ebiederm@xmission.com, nhorman@tuxdriver.com, Dan Walsh , mpatel@redhat.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 25, 2019 at 3:20 PM Richard Guy Briggs wrote: > On 2019-10-10 20:39, Paul Moore wrote: > > On Wed, Sep 18, 2019 at 9:25 PM Richard Guy Briggs wrote: > > > Add audit container identifier support to the action of signalling the > > > audit daemon. > > > > > > Since this would need to add an element to the audit_sig_info struct, > > > a new record type AUDIT_SIGNAL_INFO2 was created with a new > > > audit_sig_info2 struct. Corresponding support is required in the > > > userspace code to reflect the new record request and reply type. > > > An older userspace won't break since it won't know to request this > > > record type. > > > > > > Signed-off-by: Richard Guy Briggs > > > --- > > > include/linux/audit.h | 7 +++++++ > > > include/uapi/linux/audit.h | 1 + > > > kernel/audit.c | 28 ++++++++++++++++++++++++++++ > > > kernel/audit.h | 1 + > > > security/selinux/nlmsgtab.c | 1 + > > > 5 files changed, 38 insertions(+) > > > > > > diff --git a/include/linux/audit.h b/include/linux/audit.h > > > index 0c18d8e30620..7b640c4da4ee 100644 > > > --- a/include/linux/audit.h > > > +++ b/include/linux/audit.h > > > @@ -23,6 +23,13 @@ struct audit_sig_info { > > > char ctx[0]; > > > }; > > > > > > +struct audit_sig_info2 { > > > + uid_t uid; > > > + pid_t pid; > > > + u64 cid; > > > + char ctx[0]; > > > +}; > > > + > > > struct audit_buffer; > > > struct audit_context; > > > struct inode; > > > diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h > > > index 4ed080f28b47..693ec6e0288b 100644 > > > --- a/include/uapi/linux/audit.h > > > +++ b/include/uapi/linux/audit.h > > > @@ -72,6 +72,7 @@ > > > #define AUDIT_SET_FEATURE 1018 /* Turn an audit feature on or off */ > > > #define AUDIT_GET_FEATURE 1019 /* Get which features are enabled */ > > > #define AUDIT_CONTAINER_OP 1020 /* Define the container id and info */ > > > +#define AUDIT_SIGNAL_INFO2 1021 /* Get info auditd signal sender */ > > > > > > #define AUDIT_FIRST_USER_MSG 1100 /* Userspace messages mostly uninteresting to kernel */ > > > #define AUDIT_USER_AVC 1107 /* We filter this differently */ > > > diff --git a/kernel/audit.c b/kernel/audit.c > > > index adfb3e6a7f0c..df3db29f5a8a 100644 > > > --- a/kernel/audit.c > > > +++ b/kernel/audit.c > > > @@ -125,6 +125,7 @@ struct audit_net { > > > kuid_t audit_sig_uid = INVALID_UID; > > > pid_t audit_sig_pid = -1; > > > u32 audit_sig_sid = 0; > > > +u64 audit_sig_cid = AUDIT_CID_UNSET; > > > > > > /* Records can be lost in several ways: > > > 0) [suppressed in audit_alloc] > > > @@ -1094,6 +1095,7 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type) > > > case AUDIT_ADD_RULE: > > > case AUDIT_DEL_RULE: > > > case AUDIT_SIGNAL_INFO: > > > + case AUDIT_SIGNAL_INFO2: > > > case AUDIT_TTY_GET: > > > case AUDIT_TTY_SET: > > > case AUDIT_TRIM: > > > @@ -1257,6 +1259,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh) > > > struct audit_buffer *ab; > > > u16 msg_type = nlh->nlmsg_type; > > > struct audit_sig_info *sig_data; > > > + struct audit_sig_info2 *sig_data2; > > > char *ctx = NULL; > > > u32 len; > > > > > > @@ -1516,6 +1519,30 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh) > > > sig_data, sizeof(*sig_data) + len); > > > kfree(sig_data); > > > break; > > > + case AUDIT_SIGNAL_INFO2: > > > + len = 0; > > > + if (audit_sig_sid) { > > > + err = security_secid_to_secctx(audit_sig_sid, &ctx, &len); > > > + if (err) > > > + return err; > > > + } > > > + sig_data2 = kmalloc(sizeof(*sig_data2) + len, GFP_KERNEL); > > > + if (!sig_data2) { > > > + if (audit_sig_sid) > > > + security_release_secctx(ctx, len); > > > + return -ENOMEM; > > > + } > > > + sig_data2->uid = from_kuid(&init_user_ns, audit_sig_uid); > > > + sig_data2->pid = audit_sig_pid; > > > + if (audit_sig_sid) { > > > + memcpy(sig_data2->ctx, ctx, len); > > > + security_release_secctx(ctx, len); > > > + } > > > + sig_data2->cid = audit_sig_cid; > > > + audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO2, 0, 0, > > > + sig_data2, sizeof(*sig_data2) + len); > > > + kfree(sig_data2); > > > + break; > > > case AUDIT_TTY_GET: { > > > struct audit_tty_status s; > > > unsigned int t; > > > @@ -2384,6 +2411,7 @@ int audit_signal_info(int sig, struct task_struct *t) > > > else > > > audit_sig_uid = uid; > > > security_task_getsecid(current, &audit_sig_sid); > > > + audit_sig_cid = audit_get_contid(current); > > > } > > > > I've been wondering something as I've been working my way through > > these patches and this patch seems like a good spot to discuss this > > ... Now that we have the concept of an audit container ID "lifetime" > > in the kernel, when do we consider the ID gone? Is it when the last > > process in the container exits, or is it when we generate the last > > audit record which could possibly contain the audit container ID? > > This patch would appear to support the former, but if we wanted the > > latter we would need to grab a reference to the audit container ID > > struct so it wouldn't "die" on us before we could emit the signal info > > record. > > Are you concerned with the availability of the data when the audit > signal info record is generated, when the kernel last deals with a > particular contid or when userspace thinks there will be no more > references to it? > > I've got a bit of a dilemma with this one... > > In fact, the latter situation you describe isn't a concern at present to > be able to deliver the information since the value is copied into the > audit signal global internal variables before the signalling task dies > and the audit signal info record is created from those copied (cached) > values when requested from userspace. > > So the issue raised above I don't think is a problem. However, patch 18 > (which wasn't reviewed because it was a patch to a number of preceeding > patches) changes the reporting approach to give a chain of nested > contids which isn't reflected in the same level of reporting for the > audit signal patch/mechanism. Solving this is a bit more complex. We > could have the audit signal internal caching store a pointer to the > relevant container object and bump its refcount to ensure it doesn't > vanish until we are done with it, but the audit signal info binary > record format already has a variable length due to the selinux context > at the end of that struct and adding a second variable length element to > it would make it more complicated (but not impossible) to handle. [side note #1: Sorry for the delay, travel/conferences have limited my time and I felt we needed to focus on the larger issue of netlink/procfs first. Back to the other topics ...] [side note #2: I just realized that one can shorten "audit container ID" to ACID, I think that's going to be my favorite realization of the day :)] My concern wasn't really about the availability of the data, since as you said, it is copied into the record buffer, but rather a delay between when the audit container ID (ACID) disappears from the tracking/list db in the kernel to when it is emitted in an audit record from the kernel. During this time is seems like it could be possible for the orchestrator to reintroduce the same ACID value and if someone is not taking into account the full audit history they could get confused (the full audit history should show the proper creation/destruction events in the correct order). Ultimately I'm not sure it is a major issue, and fixing it is likely to be really ugly, but I think it would be good to add some comments in the code regarding what we guarantee as far as ACID lifetimes are concerned. -- paul moore www.paul-moore.com