From patchwork Tue Aug 2 09:10:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Artem Savkov X-Patchwork-Id: 12934412 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 880D0C19F2B for ; Tue, 2 Aug 2022 09:10:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236200AbiHBJKk (ORCPT ); Tue, 2 Aug 2022 05:10:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234911AbiHBJKj (ORCPT ); Tue, 2 Aug 2022 05:10:39 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C6D7015FF3 for ; Tue, 2 Aug 2022 02:10:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659431436; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=0Yd3q06qvhhVBLQakF8lxb418VQuM5l3HSSy3lJg+aA=; b=MfHExTy0bs/k+I79ej/vQaOlxv2dr8afat3EM9xqakHuphNRSQ2BPjgKcRMFC8qKQxaYV5 yy5NdQjKQ0/cJaSBYw2aQCTNAyVDueLSAri1UxlHnlaNy2vl2nZg/51OPZIGvbhr27ts2C ZA/VBbJWMsc5o3Ys1W0urq9NJ7nXRoQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-625-L1MPqx2HPcen8s2AbjgYyQ-1; Tue, 02 Aug 2022 05:10:33 -0400 X-MC-Unique: L1MPqx2HPcen8s2AbjgYyQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C81C1801231; Tue, 2 Aug 2022 09:10:32 +0000 (UTC) Received: from shodan.usersys.redhat.com (unknown [10.43.17.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 86E05403166; Tue, 2 Aug 2022 09:10:32 +0000 (UTC) Received: by shodan.usersys.redhat.com (Postfix, from userid 1000) id 75B691C026C; Tue, 2 Aug 2022 11:10:31 +0200 (CEST) From: Artem Savkov To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrea Arcangeli , Daniel Vacek , Jiri Olsa , Song Liu , Daniel Xu , Artem Savkov Subject: [PATCH bpf-next v2 0/3] destructive bpf_kfuncs Date: Tue, 2 Aug 2022 11:10:27 +0200 Message-Id: <20220802091030.3742334-1-asavkov@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net eBPF is often used for kernel debugging, and one of the widely used and powerful debugging techniques is post-mortem debugging with a full memory dump. Triggering a panic at exactly the right moment allows the user to get such a dump and thus a better view at the system's state. Right now the only way to do this in BPF is to signal userspace to trigger kexec/panic. This is suboptimal as going through userspace requires context changes and adds significant delays taking system further away from "the right moment". On a single-cpu system the situation is even worse because BPF program won't even be able to block the thread of interest. This patchset tries to solve this problem by allowing properly marked tracing bpf programs to call crash_kexec() kernel function. The only requirement for now to run programs calling crash_kexec() or other destructive kfuncs is CAP_SYS_BOOT capability. When signature checking for bpf programs is available it is possible that stricter rules will be applied to programs utilizing destructive kfuncs. This is a continuation of bpf_panic patchset with initial feedback taken into account. Changes in v2: - BPF_PROG_LOAD flag dropped as it doesn't fully achieve it's aim of preventing accidental execution of destructive bpf programs - selftest moved to the end of patchset - switched to kfunc destructive flag instead of a separate set Changes from RFC: - sysctl knob dropped - using crash_kexec() instead of panic() - using kfuncs instead of adding a new helper Artem Savkov (3): bpf: add destructive kfunc flag bpf: export crash_kexec() as destructive kfunc selftests/bpf: add destructive kfunc test include/linux/btf.h | 1 + kernel/bpf/verifier.c | 5 +++ kernel/kexec_core.c | 21 +++++++++++ net/bpf/test_run.c | 5 +++ .../selftests/bpf/prog_tests/kfunc_call.c | 36 +++++++++++++++++++ .../bpf/progs/kfunc_call_destructive.c | 14 ++++++++ 6 files changed, 82 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_destructive.c