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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A004FC433E2 for ; Thu, 28 May 2020 04:40:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 524C0207D3 for ; Thu, 28 May 2020 04:40:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 524C0207D3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9D7208001A; Thu, 28 May 2020 00:40:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9888680010; Thu, 28 May 2020 00:40:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 89D478001A; Thu, 28 May 2020 00:40:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0005.hostedemail.com [216.40.44.5]) by kanga.kvack.org (Postfix) with ESMTP id 7631380010 for ; Thu, 28 May 2020 00:40:02 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 18A3F2DFC for ; Thu, 28 May 2020 04:40:02 +0000 (UTC) X-FDA: 76864875444.12.shock59_74a169ea5fc4b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin12.hostedemail.com (Postfix) with ESMTP id DEC7B180555DE for ; Thu, 28 May 2020 04:40:01 +0000 (UTC) X-HE-Tag: shock59_74a169ea5fc4b X-Filterd-Recvd-Size: 2618 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Thu, 28 May 2020 04:40:01 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id C991B68B05; Thu, 28 May 2020 06:39:57 +0200 (CEST) Date: Thu, 28 May 2020 06:39:57 +0200 From: Christoph Hellwig To: Yonghong Song Cc: Andrew Morton , Christoph Hellwig , x86@kernel.org, Alexei Starovoitov , Daniel Borkmann , Masami Hiramatsu , Linus Torvalds , linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 12/23] bpf: handle the compat string in bpf_trace_copy_string better Message-ID: <20200528043957.GA28494@lst.de> References: <20200521152301.2587579-1-hch@lst.de> <20200521152301.2587579-13-hch@lst.de> <20200527190432.e4af1fba00c13cb1421f5a37@linux-foundation.org> <2b64fae6-394c-c1e5-8963-c256f4284065@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2b64fae6-394c-c1e5-8963-c256f4284065@fb.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Queue-Id: DEC7B180555DE X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, May 27, 2020 at 07:26:30PM -0700, Yonghong Song wrote: >> --- a/kernel/trace/bpf_trace.c~xxx >> +++ a/kernel/trace/bpf_trace.c >> @@ -588,15 +588,22 @@ BPF_CALL_5(bpf_seq_printf, struct seq_fi >> } >> if (fmt[i] == 's') { >> + void *unsafe_ptr; >> + >> /* try our best to copy */ >> if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) { >> err = -E2BIG; >> goto out; >> } >> - err = strncpy_from_unsafe(bufs->buf[memcpy_cnt], >> - (void *) (long) args[fmt_cnt], >> - MAX_SEQ_PRINTF_STR_LEN); >> + unsafe_ptr = (void *)(long)args[fmt_cnt]; >> + if ((unsigned long)unsafe_ptr < TASK_SIZE) { >> + err = strncpy_from_user_nofault( >> + bufs->buf[memcpy_cnt], unsafe_ptr, >> + MAX_SEQ_PRINTF_STR_LEN); >> + } else { >> + err = -EFAULT; >> + } > > This probably not right. > The pointer stored at args[fmt_cnt] is a kernel pointer, > but it could be an invalid address and we do not want to fault. > Not sure whether it exists or not, we should use > strncpy_from_kernel_nofault()? If you know it is a kernel pointer with this series it should be strncpy_from_kernel_nofault. But even before the series it should have been strncpy_from_unsafe_strict.