From patchwork Mon Jan 11 19:16:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 12011533 X-Patchwork-Delegate: bpf@iogearbox.net 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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 D1A91C433E6 for ; Mon, 11 Jan 2021 19:17:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9125D22C7E for ; Mon, 11 Jan 2021 19:17:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387724AbhAKTRy convert rfc822-to-8bit (ORCPT ); Mon, 11 Jan 2021 14:17:54 -0500 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:48696 "EHLO us-smtp-delivery-44.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387698AbhAKTRx (ORCPT ); Mon, 11 Jan 2021 14:17:53 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-356-8KY-7vDsO1ieSVcclgu1aA-1; Mon, 11 Jan 2021 14:16:58 -0500 X-MC-Unique: 8KY-7vDsO1ieSVcclgu1aA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DBA69107ACF7; Mon, 11 Jan 2021 19:16:56 +0000 (UTC) Received: from krava.redhat.com (unknown [10.40.192.185]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4BC205D9F4; Mon, 11 Jan 2021 19:16:51 +0000 (UTC) From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= Subject: [PATCH] bpf: Prevent double bpf_prog_put call from bpf_tracing_prog_attach Date: Mon, 11 Jan 2021 20:16:50 +0100 Message-Id: <20210111191650.1241578-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jolsa@kernel.org X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The bpf_tracing_prog_attach error path calls bpf_prog_put on prog, which causes refcount underflow when it's called from link_create function. link_create prog = bpf_prog_get <-- get ... tracing_bpf_link_attach(prog.. bpf_tracing_prog_attach(prog.. out_put_prog: bpf_prog_put(prog); <-- put if (ret < 0) bpf_prog_put(prog); <-- put Removing bpf_prog_put call from bpf_tracing_prog_attach and making sure its callers call it instead. Signed-off-by: Jiri Olsa Acked-by: Toke Høiland-Jørgensen Acked-by: Andrii Nakryiko --- kernel/bpf/syscall.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index c3bb03c8371f..e5999d86c76e 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2712,7 +2712,6 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog, out_put_prog: if (tgt_prog_fd && tgt_prog) bpf_prog_put(tgt_prog); - bpf_prog_put(prog); return err; } @@ -2825,7 +2824,10 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr) tp_name = prog->aux->attach_func_name; break; } - return bpf_tracing_prog_attach(prog, 0, 0); + err = bpf_tracing_prog_attach(prog, 0, 0); + if (err >= 0) + return err; + goto out_put_prog; case BPF_PROG_TYPE_RAW_TRACEPOINT: case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE: if (strncpy_from_user(buf,