From mboxrd@z Thu Jan 1 00:00:00 1970 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 17ACFC25B0E for ; Tue, 16 Aug 2022 20:55:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236675AbiHPUzr (ORCPT ); Tue, 16 Aug 2022 16:55:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233785AbiHPUzq (ORCPT ); Tue, 16 Aug 2022 16:55:46 -0400 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 467F074376 for ; Tue, 16 Aug 2022 13:55:46 -0700 (PDT) Received: by mail-pf1-x44a.google.com with SMTP id v65-20020a626144000000b0052f89472f54so4216417pfb.11 for ; Tue, 16 Aug 2022 13:55:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:references:mime-version:message-id:in-reply-to :date:from:to:cc; bh=Tnxh09mMigEObNT8d1AOsWhAz1/ozMeGIpXEVIgkx7Y=; b=E1r9/o0vUU2ivMM7W+AZ6k7lK/mBTiLQceLw2XRFWxAFs+1iXzHTxF5vfe4Y1vV3cL kIPf4uBI0iNjd3WuYSHNECs2/CC6fwh2DgkSRnxh1V9myuzEkfQdJRw7J0la6mAsmmR+ AtWvJ/IJewHpUeQyQ2BlnrOpO7Xqya/tWMasAkZpgCNrMRmoys4QN5OoXkmeJdLoCvOj FDqMNITTc2XjHsSL31fqhxCHqx+HCwA9j6h+ufIqcSbGs0fed0IJOSkYueyPTkcZgqqt YHQmq0Ioj2/zr7od+qRea42Cf0SP8AK8dqvrr7GZyOfRYYPCbaCr/e9i6/yNUzKq0iy5 6Plg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:references:mime-version:message-id:in-reply-to :date:x-gm-message-state:from:to:cc; bh=Tnxh09mMigEObNT8d1AOsWhAz1/ozMeGIpXEVIgkx7Y=; b=rB3WFl0L+r3NSBLmoTdFv+kR+V8+iEeq8p/C6w9wySJkeUdP/3nzAmrPF0QDtNDHpq KnNgBHefZ+vjeTU2cpJKF0MVdj7aH5EnpnSFDRaws3Ks6WAzE3YIbMfRuElUa++xGLyo Olb8TixwDA7G+1gIhAILottzRK+G3AgHnBdbVQpCU5o8J01HumOkqGGubLbPYLlNg6zO 5SUPTMTY8RlWluXIxvFRlpJtaBLWdJTSkVjxld2vjN6M7R7iLgueIAX5NFszV4vwVtQ8 jOPTrpZG3RqlBckzQm7LbwfYRW4W5sSOJbxTAH/X2t4ai3ghfA55RFiO2QrZNUMO+LkY 4KrQ== X-Gm-Message-State: ACgBeo2IXdhqJab7nR7uGAEYMZ9X/iJS64GC1EvqzQ9S4vTgXuL8Dj5V t24ikpcW1HGO3RifKqtAWUCJnDlLR2qwQXh/QBN1anHRo72HNeaUBsRU/dPut5TrTiYlTUJF9qp 6rXeIn2ePgJoNCBivP/klrkyw4j5MgI/SyrtJ4uc9MHRoq9ZAq2dMDp7FCy9Gqag= X-Google-Smtp-Source: AA6agR4kh46MfTnNmY7hWP81gqMBgXm5cam87S6Es8noSzU4cYxWReBe+XMNXF/oqNh1EvxwKx0vuh6G7ffXqg== X-Received: from zhuyifei-kvm.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2edc]) (user=zhuyifei job=sendgmr) by 2002:aa7:88d3:0:b0:52e:ade6:6192 with SMTP id k19-20020aa788d3000000b0052eade66192mr22776201pff.41.1660683345768; Tue, 16 Aug 2022 13:55:45 -0700 (PDT) Date: Tue, 16 Aug 2022 20:55:17 +0000 In-Reply-To: <20220816205517.682470-1-zhuyifei@google.com> Message-Id: <20220816205517.682470-2-zhuyifei@google.com> Mime-Version: 1.0 References: <20220816205517.682470-1-zhuyifei@google.com> X-Mailer: git-send-email 2.37.1.595.g718a3a8f04-goog Subject: [PATCH bpf 2/2] bpf: Add WARN_ON for recursive prog_run invocation From: YiFei Zhu To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Jinghao Jia , Daniel Borkmann , Alexei Starovoitov , Andrii Nakryiko , Song Liu , Stanislav Fomichev , Jason Zhang , Jann Horn , mvle@us.ibm.com, zohar@linux.ibm.com, tyxu.uiuc@gmail.com, security@kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Recursive invocation should not happen after commit 86f44fcec22c ("bpf: Disallow bpf programs call prog_run command."), unlike what is suggested in the comment. The only way to I can see this condition trigger is if userspace fetches an fd of a kernel-loaded lskel and attempt to race the kernel to execute that lskel... which also shouldn't happen under normal circumstances. To make this "should never happen" explicit, clarify this in the comment and add a WARN_ON. Fixes: 86f44fcec22c ("bpf: Disallow bpf programs call prog_run command.") Signed-off-by: YiFei Zhu --- kernel/bpf/syscall.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 27760627370d..9cac9402c0bf 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -5119,8 +5119,8 @@ int kern_sys_bpf(int cmd, union bpf_attr *attr, unsigned int size) run_ctx.bpf_cookie = 0; run_ctx.saved_run_ctx = NULL; - if (!__bpf_prog_enter_sleepable(prog, &run_ctx)) { - /* recursion detected */ + if (WARN_ON(!__bpf_prog_enter_sleepable(prog, &run_ctx))) { + /* recursion detected, should never happen */ bpf_prog_put(prog); return -EBUSY; } -- 2.37.1.595.g718a3a8f04-goog