From patchwork Tue Apr 27 22:41:56 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 429158 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=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 CC197C43460 for ; Tue, 27 Apr 2021 22:42:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A87346105A for ; Tue, 27 Apr 2021 22:42:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236817AbhD0Wmv convert rfc822-to-8bit (ORCPT ); Tue, 27 Apr 2021 18:42:51 -0400 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:43961 "EHLO us-smtp-delivery-44.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235420AbhD0Wmv (ORCPT ); Tue, 27 Apr 2021 18:42:51 -0400 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-192-WtPfqhlBMCqXJZwPGjXKvw-1; Tue, 27 Apr 2021 18:42:01 -0400 X-MC-Unique: WtPfqhlBMCqXJZwPGjXKvw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CDDC3805EF8; Tue, 27 Apr 2021 22:41:59 +0000 (UTC) Received: from krava.cust.in.nbox.cz (unknown [10.40.192.163]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7E18310027A5; Tue, 27 Apr 2021 22:41:57 +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 Subject: [PATCH] bpf: Fix recursion check in trampoline Date: Wed, 28 Apr 2021 00:41:56 +0200 Message-Id: <20210427224156.708231-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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: netdev@vger.kernel.org The recursion check in __bpf_prog_enter and __bpf_prog_exit leaves some (not inlined) functions unprotected: In __bpf_prog_enter: - migrate_disable is called before prog->active is checked In __bpf_prog_exit: - migrate_enable,rcu_read_unlock_strict are called after prog->active is decreased When attaching trampoline to them we get panic like: traps: PANIC: double fault, error_code: 0x0 double fault: 0000 [#1] SMP PTI RIP: 0010:__bpf_prog_enter+0x4/0x50 ... Call Trace: bpf_trampoline_6442466513_0+0x18/0x1000 migrate_disable+0x5/0x50 __bpf_prog_enter+0x9/0x50 bpf_trampoline_6442466513_0+0x18/0x1000 migrate_disable+0x5/0x50 __bpf_prog_enter+0x9/0x50 bpf_trampoline_6442466513_0+0x18/0x1000 migrate_disable+0x5/0x50 __bpf_prog_enter+0x9/0x50 bpf_trampoline_6442466513_0+0x18/0x1000 migrate_disable+0x5/0x50 ... Making the recursion check before the rest of the calls in __bpf_prog_enter and as last call in __bpf_prog_exit. Signed-off-by: Jiri Olsa --- kernel/bpf/trampoline.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 4aa8b52adf25..301735f7e88e 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -558,12 +558,12 @@ static void notrace inc_misses_counter(struct bpf_prog *prog) u64 notrace __bpf_prog_enter(struct bpf_prog *prog) __acquires(RCU) { - rcu_read_lock(); - migrate_disable(); if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) { inc_misses_counter(prog); return 0; } + rcu_read_lock(); + migrate_disable(); return bpf_prog_start_time(); } @@ -590,10 +590,12 @@ static void notrace update_prog_stats(struct bpf_prog *prog, void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start) __releases(RCU) { - update_prog_stats(prog, start); + if (start) { + update_prog_stats(prog, start); + migrate_enable(); + rcu_read_unlock(); + } __this_cpu_dec(*(prog->active)); - migrate_enable(); - rcu_read_unlock(); } u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog)