From patchwork Thu Nov 5 02:25:38 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Xu X-Patchwork-Id: 11882995 X-Patchwork-Delegate: bpf@iogearbox.net 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=-12.8 required=3.0 tests=BAYES_00,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=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 97DABC2D0A3 for ; Thu, 5 Nov 2020 02:26:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 381BC206ED for ; Thu, 5 Nov 2020 02:26:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=dxuuu.xyz header.i=@dxuuu.xyz header.b="NHLemwZ2"; dkim=temperror (0-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="PqvG9s5K" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728301AbgKEC0L (ORCPT ); Wed, 4 Nov 2020 21:26:11 -0500 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:50127 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387593AbgKEC0J (ORCPT ); Wed, 4 Nov 2020 21:26:09 -0500 Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id 7ACA85C01CA; Wed, 4 Nov 2020 21:26:08 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute3.internal (MEProxy); Wed, 04 Nov 2020 21:26:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=dxuuu.xyz; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; s=fm1; bh=d921gZrveLgVW 10+cFYgvJSXNaGtEusR13nH1+m1Jf0=; b=NHLemwZ2SFJVN2DDESiS+inFiQTxo qozfwGi1E4c/jSGV5fN/iXRqHyd1Ot3fCXgsPhpEDC+HQyyewpnsKj5tRsxcUdK/ nYn4YPCZebptPuqGxizveVIbFW20E4YgCEpajJL555BTU0IzjBggYRp6LJuJ1aFi oL4HdSKlGwB3f//JA/MnsCqym9HUQIdSkkLEdBXmRyiE95YoMVRK+6Z3ffENd0v6 eodXi29zfOp9rNboh0nEX3hTC5Q6J7bRzehdrgF11iszGM/sMlUu2/oycm9Ahzk8 0L9xqK1fHEzeThMgz0boO2cZfAd4107U9uOt0PFj2jfykDSw92R4bQhsA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:date:from :in-reply-to:message-id:mime-version:references:subject:to :x-me-proxy:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s= fm1; bh=d921gZrveLgVW10+cFYgvJSXNaGtEusR13nH1+m1Jf0=; b=PqvG9s5K hay7O1tv73p3Y7tBEWNLWfU7RFtb1XnZVILYE34g42SqCoxa2W6Fugs967Mvtjz3 +ePu27QYMee5D0Uv7j0Mo/aMLUW1Su8hawM2OpfHVZIVJANX1ffoTVF9SaqO++KL uVJFEPROZ/FbTSnPp7+IyAuuPI93K6T/BJCmLmmF9zKNs7NeYauwbNIPWzZlbSqK jRJAm9Owd3cqxbiLA88JW2JLaODXTCWqJBzDUeVwRi3jVTkbPUUhXR4fiPo4FGkq dEtuJ/R04/k2s3gXz9XuSWSVLpjVzGPJP4kzLdoGgBWFiKPM55WJ/QcHhpXYY6wL A8cYHIrPm0wSsg== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedujedruddtiedggeejucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucgfrhhlucfvnfffucdljedtmdenucfjughrpefhvf fufffkofgjfhgggfestdekredtredttdenucfhrhhomhepffgrnhhivghlucgiuhcuoegu gihusegugihuuhhurdighiiiqeenucggtffrrghtthgvrhhnpefgkeduleekhfetvefhge fgvdegfeejfefguedvuddthffggffhhedtueeuteefieenucfkphepieelrddukedurddu tdehrdeigeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhroh hmpegugihusegugihuuhhurdighiii X-ME-Proxy: Received: from localhost.localdomain (c-69-181-105-64.hsd1.ca.comcast.net [69.181.105.64]) by mail.messagingengine.com (Postfix) with ESMTPA id A37AA32801D7; Wed, 4 Nov 2020 21:26:07 -0500 (EST) From: Daniel Xu To: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net Cc: Daniel Xu , kernel-team@fb.com Subject: [PATCH bpf v2 2/2] selftest/bpf: Test bpf_probe_read_user_str() strips trailing bytes after NUL Date: Wed, 4 Nov 2020 18:25:38 -0800 Message-Id: <4e3e8b9b525c8bed39c0ee2aa68f2dff701f56a4.1604542786.git.dxu@dxuuu.xyz> X-Mailer: git-send-email 2.28.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Previously, bpf_probe_read_user_str() could potentially overcopy the trailing bytes after the NUL due to how do_strncpy_from_user() does the copy in long-sized strides. The issue has been fixed in the previous commit. This commit adds a selftest that ensures we don't regress bpf_probe_read_user_str() again. Signed-off-by: Daniel Xu --- .../bpf/prog_tests/probe_read_user_str.c | 60 +++++++++++++++++++ .../bpf/progs/test_probe_read_user_str.c | 34 +++++++++++ 2 files changed, 94 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/probe_read_user_str.c create mode 100644 tools/testing/selftests/bpf/progs/test_probe_read_user_str.c diff --git a/tools/testing/selftests/bpf/prog_tests/probe_read_user_str.c b/tools/testing/selftests/bpf/prog_tests/probe_read_user_str.c new file mode 100644 index 000000000000..597a166e6c8d --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/probe_read_user_str.c @@ -0,0 +1,60 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include "test_probe_read_user_str.skel.h" + +static const char str[] = "mestring"; + +void test_probe_read_user_str(void) +{ + struct test_probe_read_user_str *skel; + int fd, err, duration = 0; + char buf[256]; + ssize_t n; + + skel = test_probe_read_user_str__open_and_load(); + if (CHECK(!skel, "test_probe_read_user_str__open_and_load", + "skeleton open and load failed\n")) + goto out; + + err = test_probe_read_user_str__attach(skel); + if (CHECK(err, "test_probe_read_user_str__attach", + "skeleton attach failed: %d\n", err)) + goto out; + + fd = open("/dev/null", O_WRONLY); + if (CHECK(fd < 0, "open", "open /dev/null failed: %d\n", fd)) + goto out; + + /* Give pid to bpf prog so it doesn't read from anyone else */ + skel->bss->pid = getpid(); + + /* Ensure bytes after string are ones */ + memset(buf, 1, sizeof(buf)); + memcpy(buf, str, sizeof(str)); + + /* Trigger tracepoint */ + n = write(fd, buf, sizeof(buf)); + if (CHECK(n != sizeof(buf), "write", "write failed: %ld\n", n)) + goto fd_out; + + /* Did helper fail? */ + if (CHECK(skel->bss->ret < 0, "prog ret", "prog returned: %d\n", + skel->bss->ret)) + goto fd_out; + + /* Check that string was copied correctly */ + err = memcmp(skel->bss->buf, str, sizeof(str)); + if (CHECK(err, "memcmp", "prog copied wrong string")) + goto fd_out; + + /* Now check that no extra trailing bytes were copied */ + memset(buf, 0, sizeof(buf)); + err = memcmp(skel->bss->buf + sizeof(str), buf, sizeof(buf) - sizeof(str)); + if (CHECK(err, "memcmp", "trailing bytes were not stripped")) + goto fd_out; + +fd_out: + close(fd); +out: + test_probe_read_user_str__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_probe_read_user_str.c b/tools/testing/selftests/bpf/progs/test_probe_read_user_str.c new file mode 100644 index 000000000000..41c3e296566e --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_probe_read_user_str.c @@ -0,0 +1,34 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include + +#include + +struct sys_enter_write_args { + unsigned long long pad; + int syscall_nr; + int pad1; /* 4 byte hole */ + unsigned int fd; + int pad2; /* 4 byte hole */ + const char *buf; + size_t count; +}; + +pid_t pid = 0; +int ret = 0; +char buf[256] = {}; + +SEC("tracepoint/syscalls/sys_enter_write") +int on_write(struct sys_enter_write_args *ctx) +{ + if (pid != (bpf_get_current_pid_tgid() >> 32)) + return 0; + + ret = bpf_probe_read_user_str(buf, sizeof(buf), ctx->buf); + + return 0; +} + +char _license[] SEC("license") = "GPL";