From patchwork Tue Jan 24 11:31:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 63616 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 776893858C50 for ; Tue, 24 Jan 2023 11:32:21 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 776893858C50 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1674559941; bh=PJPgxUgYr8rHNm/qv3ncL90lrz/h5m46pt5SaoLyXik=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=SwlO3CEq3mi4AQ5ZHstwnfbNJink7DO0ozn35ds0TDlviArNVrMjFCbkbVwdhdCS4 KVNhwUe5v3Jf/3tlsT7J0wzVO8MwJ8lwIbmDO7f4Nt2H7PXO49XUiRPRxVgiRe4EQx G8tggzWgfmUas1EWJe27oA4GA3Ljx2IZPMH5OHe4= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id F1F903858D28 for ; Tue, 24 Jan 2023 11:31:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org F1F903858D28 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-481-rlKGUI46NmSG01q94HxHIg-1; Tue, 24 Jan 2023 06:31:58 -0500 X-MC-Unique: rlKGUI46NmSG01q94HxHIg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 296C81871D94 for ; Tue, 24 Jan 2023 11:31:58 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.194.74]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4F7B453A0 for ; Tue, 24 Jan 2023 11:31:57 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH] stdio-common: Handle -1 buffer size in __sprintf_chk & co (bug 30039) Date: Tue, 24 Jan 2023 12:31:55 +0100 Message-ID: <874jsggod0.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-10.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Florian Weimer via Libc-alpha From: Florian Weimer Reply-To: Florian Weimer Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" This shows up as an assertion failure when sprintf is called with a specifier like "%.8g" and libquadmath is linked in: Fatal glibc error: printf_buffer_as_file.c:31 (__printf_buffer_as_file_commit): assertion failed: file->stream._IO_write_ptr <= file->next->write_end Fix this by detecting pointer wraparound in __vsprintf_internal and saturate the addition to the end of the address space instead. Tested on i686-linux-gnu, x86_64-linux-gnu. Proposed as a release blocker. Reviewed-by: Carlos O'Donell Tested-by: Carlos O'Donell --- debug/Makefile | 5 ++ debug/tst-sprintf-fortify-unchecked.c | 126 ++++++++++++++++++++++++++++++++++ include/printf_buffer.h | 19 +++-- libio/iovsprintf.c | 15 ++-- 4 files changed, 155 insertions(+), 10 deletions(-) base-commit: 103a469dc7755fd9e8ccf362f3dd4c55dc761908 diff --git a/debug/Makefile b/debug/Makefile index 13f15d15d3..52f9a7852c 100644 --- a/debug/Makefile +++ b/debug/Makefile @@ -200,6 +200,10 @@ LDFLAGS-tst-backtrace6 = -rdynamic CFLAGS-tst-ssp-1.c += -fstack-protector-all +# Disable compiler optimizations around vsprintf (the function under test). +CFLAGS-tst-sprintf-fortify-unchecked.c = \ + -fno-builtin-vsprintf -fno-builtin-__vsprintf_chk + tests = backtrace-tst \ tst-longjmp_chk \ test-strcpy_chk \ @@ -211,6 +215,7 @@ tests = backtrace-tst \ tst-backtrace5 \ tst-backtrace6 \ tst-realpath-chk \ + tst-sprintf-fortify-unchecked \ $(tests-all-chk) tests-time64 += \ diff --git a/debug/tst-sprintf-fortify-unchecked.c b/debug/tst-sprintf-fortify-unchecked.c new file mode 100644 index 0000000000..7c7bd1b5e4 --- /dev/null +++ b/debug/tst-sprintf-fortify-unchecked.c @@ -0,0 +1,126 @@ +/* Tests for fortified sprintf with unknown buffer bounds (bug 30039). + Copyright (C) 2023 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include +#include +#include + +/* This test is not built with _FORTIFY_SOURCE. Instead it calls the + appropriate implementation directly. The fortify mode is specified + in this variable. */ +static int fortify_mode; + +/* This does not handle long-double redirects etc., but we test only + format strings that stay within the confines of the base + implementation. */ +int __vsprintf_chk (char *s, int flag, size_t slen, const char *format, + va_list ap); + +/* Invoke vsprintf or __vsprintf_chk according to fortify_mode. */ +static int +my_vsprintf (char *buf, const char *format, va_list ap) +{ + int result; + if (fortify_mode == 0) + result = vsprintf (buf, format, ap); + else + /* Call the fortified version with an unspecified length. */ + result = __vsprintf_chk (buf, fortify_mode - 1, -1, format, ap); + return result; +} + +/* Run one test, with the specified expected output. */ +static void __attribute ((format (printf, 2, 3))) +do_check (const char *expected, const char *format, ...) +{ + va_list ap; + va_start (ap, format); + + char buf_expected[24]; + memset (buf_expected, '@', sizeof (buf_expected)); + TEST_VERIFY (strlen (expected) < sizeof (buf_expected)); + strcpy (buf_expected, expected); + + char buf[sizeof (buf_expected)]; + memset (buf, '@', sizeof (buf)); + + int ret = my_vsprintf (buf, format, ap); + TEST_COMPARE_BLOB (buf_expected, sizeof (buf_expected), buf, sizeof (buf)); + TEST_COMPARE (ret, strlen (expected)); + + va_end (ap); +} + +/* Run the tests in all fortify modes. */ +static void +do_tests (void) +{ + for (fortify_mode = 0; fortify_mode <= 3; ++fortify_mode) + { + do_check ("0", "%d", 0); + do_check ("-2147483648", "%d", -2147483647 - 1); + do_check ("-9223372036854775808", "%lld", -9223372036854775807LL - 1); + do_check ("", "%s", ""); + do_check (" ", "%22s", ""); + do_check ("XXXXXXXXXXXXXXXXXXXXXX", "%s", "XXXXXXXXXXXXXXXXXXXXXX"); + do_check ("1.125000", "%f", 1.125); + do_check ("1.125", "%g", 1.125); + do_check ("1.125", "%.8g", 1.125); + } +} + +/* printf callback that falls back to the glibc-supplied + implementation. */ +static int +dummy_printf_function (FILE *__stream, + const struct printf_info *__info, + const void *const *__args) +{ + return -2; /* Request fallback. */ +} + +/* Likewise for the type information. */ +static int +dummy_arginfo_function (const struct printf_info *info, + size_t n, int *argtypes, int *size) +{ + return -1; /* Request fallback. */ +} + +static int +do_test (void) +{ + do_tests (); + + /* Activate __printf_function_invoke mode. */ + register_printf_specifier ('d', dummy_printf_function, + dummy_arginfo_function); + register_printf_specifier ('g', dummy_printf_function, + dummy_arginfo_function); + register_printf_specifier ('s', dummy_printf_function, + dummy_arginfo_function); + + /* Rerun the tests with callback functions. */ + do_tests (); + + return 0; +} + +#include diff --git a/include/printf_buffer.h b/include/printf_buffer.h index 55feebf279..4d787e4b2c 100644 --- a/include/printf_buffer.h +++ b/include/printf_buffer.h @@ -115,17 +115,26 @@ __printf_buffer_has_failed (struct __printf_buffer *buf) return buf->mode == __printf_buffer_mode_failed; } +/* Initialization of a buffer, using the memory region from [BASE, + END) as the initial buffer contents. */ +static inline void +__printf_buffer_init_end (struct __printf_buffer *buf, char *base, char *end, + enum __printf_buffer_mode mode) +{ + buf->write_base = base; + buf->write_ptr = base; + buf->write_end = end; + buf->written = 0; + buf->mode = mode; +} + /* Initialization of a buffer, using the memory region from [BASE, BASE +LEN) as the initial buffer contents. LEN can be zero. */ static inline void __printf_buffer_init (struct __printf_buffer *buf, char *base, size_t len, enum __printf_buffer_mode mode) { - buf->write_base = base; - buf->write_ptr = base; - buf->write_end = base + len; - buf->written = 0; - buf->mode = mode; + __printf_buffer_init_end (buf, base, base + len, mode); } /* Called by printf_buffer_putc for a full buffer. */ diff --git a/libio/iovsprintf.c b/libio/iovsprintf.c index 8d53e401cc..9a4f59a06e 100644 --- a/libio/iovsprintf.c +++ b/libio/iovsprintf.c @@ -45,14 +45,19 @@ __vsprintf_internal (char *string, size_t maxlen, if ((mode_flags & PRINTF_CHK) != 0) { string[0] = '\0'; - __printf_buffer_init (&buf, string, maxlen, + /* In some cases, __sprintf_chk is called with an unknown buffer + size (the special value -1). Prevent pointer wraparound in + this case and saturate to the end of the address space. */ + uintptr_t end; + if (__builtin_add_overflow ((uintptr_t) string, maxlen, &end)) + end = -1; + __printf_buffer_init_end (&buf, string, (char *) end, __printf_buffer_mode_sprintf_chk); } else - { - __printf_buffer_init (&buf, string, 0, __printf_buffer_mode_sprintf); - buf.write_end = (char *) ~(uintptr_t) 0; /* End of address space. */ - } + /* Use end of address space. */ + __printf_buffer_init_end (&buf, string, (char *) ~(uintptr_t) 0, + __printf_buffer_mode_sprintf); __printf_buffer (&buf, format, args, mode_flags);