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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 A617BC5DF61 for ; Thu, 7 Nov 2019 05:47:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A7BC214D8 for ; Thu, 7 Nov 2019 05:47:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573105655; bh=o1O/+AJoW1BkQ0HZpEDJbcWmnyV2M2ZxyvbEdboY968=; h=From:To:CC:Subject:Date:In-Reply-To:References:List-ID:From; b=wfGk7Ns3cAUsTX7dRwxTlytN0ZYiFwAifw1Mub1NIiMcBNJcydMZRurZs6MFogMLW J1wsaY2WfSWwoY1voHhZ34QUKBwqO2u6ZQzzsef6GVBvcqEq9h5dEkGHuN+rkYXRT2 btCDibis/B93OIaKkg4s2eXzBi8Dz85z/wSiGlf0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726958AbfKGFrf convert rfc822-to-8bit (ORCPT ); Thu, 7 Nov 2019 00:47:35 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:11534 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726565AbfKGFrf (ORCPT ); Thu, 7 Nov 2019 00:47:35 -0500 Received: from pps.filterd (m0109332.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id xA75i6fu016010 for ; Wed, 6 Nov 2019 21:47:33 -0800 Received: from mail.thefacebook.com (mailout.thefacebook.com [199.201.64.23]) by mx0a-00082601.pphosted.com with ESMTP id 2w41u0kgxc-6 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Wed, 06 Nov 2019 21:47:33 -0800 Received: from 2401:db00:12:909f:face:0:3:0 (2620:10d:c081:10::13) by mail.thefacebook.com (2620:10d:c081:35::129) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA) id 15.1.1713.5; Wed, 6 Nov 2019 21:47:09 -0800 Received: by devbig007.ftw2.facebook.com (Postfix, from userid 572438) id BB699760BC0; Wed, 6 Nov 2019 21:47:08 -0800 (PST) Smtp-Origin-Hostprefix: devbig From: Alexei Starovoitov Smtp-Origin-Hostname: devbig007.ftw2.facebook.com To: CC: , , , , Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v2 bpf-next 12/17] bpf: Fix race in btf_resolve_helper_id() Date: Wed, 6 Nov 2019 21:46:39 -0800 Message-ID: <20191107054644.1285697-13-ast@kernel.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191107054644.1285697-1-ast@kernel.org> References: <20191107054644.1285697-1-ast@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-11-06_09:2019-11-06,2019-11-06 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 suspectscore=1 bulkscore=0 clxscore=1015 priorityscore=1501 adultscore=0 lowpriorityscore=0 mlxscore=0 spamscore=0 impostorscore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1911070059 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org btf_resolve_helper_id() caching logic is racy, since under root the verifier can verify several programs in parallel. Fix it with extra spin_lock. Fixes: a7658e1a4164 ("bpf: Check types of arguments passed into helpers") Signed-off-by: Alexei Starovoitov --- include/linux/bpf.h | 3 ++- kernel/bpf/btf.c | 34 +++++++++++++++++++++++++++++++++- kernel/bpf/verifier.c | 6 +----- 3 files changed, 36 insertions(+), 7 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 9206b7e86dde..c287dfce2a17 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -874,7 +874,8 @@ int btf_struct_access(struct bpf_verifier_log *log, const struct btf_type *t, int off, int size, enum bpf_access_type atype, u32 *next_btf_id); -u32 btf_resolve_helper_id(struct bpf_verifier_log *log, void *, int); +u32 btf_resolve_helper_id(struct bpf_verifier_log *log, + const struct bpf_func_proto *fn, int); int btf_distill_func_proto(struct bpf_verifier_log *log, struct btf *btf, diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 78d9ceaabc00..7155787a0b13 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3584,7 +3584,8 @@ int btf_struct_access(struct bpf_verifier_log *log, return -EINVAL; } -u32 btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, int arg) +static u32 __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, + int arg) { char fnname[KSYM_SYMBOL_LEN + 4] = "btf_"; const struct btf_param *args; @@ -3652,6 +3653,37 @@ u32 btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, int arg) return btf_id; } +static DEFINE_SPINLOCK(btf_resolve_lock); + +u32 btf_resolve_helper_id(struct bpf_verifier_log *log, + const struct bpf_func_proto *fn, int arg) +{ + u32 *btf_id = &fn->btf_id[arg]; + u32 ret; + + if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID) + return -EINVAL; + + if (*btf_id) + /* ok to do without lock. It only set once */ + return *btf_id; + /* ok to race the search. The result is the same */ + ret = __btf_resolve_helper_id(log, fn->func, arg); + if (!ret) { + bpf_log(log, "BTF resolution bug\n"); + return -EFAULT; + } + spin_lock(&btf_resolve_lock); + if (*btf_id) { + ret = *btf_id; + goto out; + } + *btf_id = ret; +out: + spin_unlock(&btf_resolve_lock); + return ret; +} + static int __get_type_size(struct btf *btf, u32 btf_id, const struct btf_type **bad_type) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 36542edd4936..c4fd11a27d81 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4147,11 +4147,7 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn meta.func_id = func_id; /* check args */ for (i = 0; i < 5; i++) { - if (fn->arg_type[i] == ARG_PTR_TO_BTF_ID) { - if (!fn->btf_id[i]) - fn->btf_id[i] = btf_resolve_helper_id(&env->log, fn->func, i); - meta.btf_id = fn->btf_id[i]; - } + meta.btf_id = btf_resolve_helper_id(&env->log, fn, i); err = check_func_arg(env, BPF_REG_1 + i, fn->arg_type[i], &meta); if (err) return err; -- 2.23.0