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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 0067FC433E0 for ; Fri, 29 May 2020 00:48:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE8C52075F for ; Fri, 29 May 2020 00:48:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="Mh1rhlb4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438131AbgE2AsS (ORCPT ); Thu, 28 May 2020 20:48:18 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:6552 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2438114AbgE2AsR (ORCPT ); Thu, 28 May 2020 20:48:17 -0400 Received: from pps.filterd (m0089730.ppops.net [127.0.0.1]) by m0089730.ppops.net (8.16.0.42/8.16.0.42) with SMTP id 04T0iQkq018064 for ; Thu, 28 May 2020 17:48:15 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=facebook; bh=XKaNCUf4aWfVxow/sVN7utvio0I/teUXWg+FJPTB7ys=; b=Mh1rhlb4PIve3IbnuPTXHwOn/Ox0oWd2IWDTu+DoYk6x7hyeSvURkoGHRePqn+F+JStc zOSio62x/co/4AXyRQhrxnUUro1tWXCPSmlWmSOXBP+fFspRdCEhOzs3SKFVukPGAPKz ITTe2XcZzX3rM9tSGf+4asHsS3g6jTdwVNE= Received: from maileast.thefacebook.com ([163.114.130.16]) by m0089730.ppops.net with ESMTP id 31a24ubyfx-5 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 28 May 2020 17:48:15 -0700 Received: from intmgw004.08.frc2.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Thu, 28 May 2020 17:48:14 -0700 Received: by devbig003.ftw2.facebook.com (Postfix, from userid 128203) id C61D23704D0A; Thu, 28 May 2020 17:48:10 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Yonghong Song Smtp-Origin-Hostname: devbig003.ftw2.facebook.com To: CC: Alexei Starovoitov , Daniel Borkmann , , Christoph Hellwig Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH bpf-next] bpf: use strncpy_from_unsafe_strict() in bpf_seq_printf() helper Date: Thu, 28 May 2020 17:48:10 -0700 Message-ID: <20200529004810.3352219-1-yhs@fb.com> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-05-28_08:2020-05-28,2020-05-28 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 impostorscore=0 bulkscore=0 phishscore=0 spamscore=0 clxscore=1015 suspectscore=1 priorityscore=1501 mlxlogscore=999 lowpriorityscore=0 cotscore=-2147483648 adultscore=0 mlxscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005290003 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org In bpf_seq_printf() helper, when user specified a "%s" in the format string, strncpy_from_unsafe() is used to read the actual string to a buffer. The string could be a format string or a string in the kernel data structure. It is really unlikely that the string will reside in the user memory. This is different from Commit b2a5212fb634 ("bpf: Restrict bpf_trace_prin= tk()'s %s usage and add %pks, %pus specifier") which still used strncpy_from_unsafe() for "%s" to preserve the old behavior. If in the future, bpf_seq_printf() indeed needs to read user memory, we can implement "%pus" format string. Based on discussion in [1], if the intent is to read kernel memory, strncpy_from_unsafe_strict() should be used. So this patch changed to use strncpy_from_unsafe_strict(). [1]: https://lore.kernel.org/bpf/20200521152301.2587579-1-hch@lst.de/T/ Cc: Christoph Hellwig Signed-off-by: Yonghong Song --- kernel/trace/bpf_trace.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 187cd6995bbb..3a4afbc7f0bc 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -585,9 +585,9 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char= *, fmt, u32, fmt_size, goto out; } =20 - err =3D strncpy_from_unsafe(bufs->buf[memcpy_cnt], - (void *) (long) args[fmt_cnt], - MAX_SEQ_PRINTF_STR_LEN); + err =3D strncpy_from_unsafe_strict(bufs->buf[memcpy_cnt], + (void *) (long) args[fmt_cnt], + MAX_SEQ_PRINTF_STR_LEN); if (err < 0) bufs->buf[memcpy_cnt][0] =3D '\0'; params[fmt_cnt] =3D (u64)(long)bufs->buf[memcpy_cnt]; --=20 2.24.1