From patchwork Mon Jul 12 06:08:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 476355 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, 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 65F60C07E99 for ; Mon, 12 Jul 2021 06:20:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 444A461130 for ; Mon, 12 Jul 2021 06:20:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234132AbhGLGXY (ORCPT ); Mon, 12 Jul 2021 02:23:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:38964 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234046AbhGLGWY (ORCPT ); Mon, 12 Jul 2021 02:22:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7B3976115B; Mon, 12 Jul 2021 06:19:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626070748; bh=EFGsEEDOYaq3aXmYpaqZFq9m2kjdxBvkefvNV+v+XVQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pZkz9x/Od32ZGuTa3i2ewP4XJudFEnSWPZR78sk6j32ENSIr/Voy4qdf3sSzLgmlh k1JLf2ZBESq7BI43c7bv5dtxoo2uV439W2Z43fr5wa2RZlt1aIpw+310vKYXNPWO3C Chr19pDn8pjkIvln0ZyVKyKAaPfzrXg8hIvXQh1c= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Richard Fitzgerald , Petr Mladek , Sasha Levin Subject: [PATCH 5.4 116/348] lib: vsprintf: Fix handling of number field widths in vsscanf Date: Mon, 12 Jul 2021 08:08:20 +0200 Message-Id: <20210712060716.875803788@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060659.886176320@linuxfoundation.org> References: <20210712060659.886176320@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Richard Fitzgerald [ Upstream commit 900fdc4573766dd43b847b4f54bd4a1ee2bc7360 ] The existing code attempted to handle numbers by doing a strto[u]l(), ignoring the field width, and then repeatedly dividing to extract the field out of the full converted value. If the string contains a run of valid digits longer than will fit in a long or long long, this would overflow and no amount of dividing can recover the correct value. This patch fixes vsscanf() to obey number field widths when parsing the number. A new _parse_integer_limit() is added that takes a limit for the number of characters to parse. The number field conversion in vsscanf is changed to use this new function. If a number starts with a radix prefix, the field width must be long enough for at last one digit after the prefix. If not, it will be handled like this: sscanf("0x4", "%1i", &i): i=0, scanning continues with the 'x' sscanf("0x4", "%2i", &i): i=0, scanning continues with the '4' This is consistent with the observed behaviour of userland sscanf. Note that this patch does NOT fix the problem of a single field value overflowing the target type. So for example: sscanf("123456789abcdef", "%x", &i); Will not produce the correct result because the value obviously overflows INT_MAX. But sscanf will report a successful conversion. Note that where a very large number is used to mean "unlimited", the value INT_MAX is used for consistency with the behaviour of vsnprintf(). Signed-off-by: Richard Fitzgerald Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210514161206.30821-2-rf@opensource.cirrus.com Signed-off-by: Sasha Levin --- lib/kstrtox.c | 13 ++++++-- lib/kstrtox.h | 2 ++ lib/vsprintf.c | 82 +++++++++++++++++++++++++++++--------------------- 3 files changed, 60 insertions(+), 37 deletions(-) diff --git a/lib/kstrtox.c b/lib/kstrtox.c index 1006bf70bf74..95c7234ad467 100644 --- a/lib/kstrtox.c +++ b/lib/kstrtox.c @@ -39,20 +39,22 @@ const char *_parse_integer_fixup_radix(const char *s, unsigned int *base) /* * Convert non-negative integer string representation in explicitly given radix - * to an integer. + * to an integer. A maximum of max_chars characters will be converted. + * * Return number of characters consumed maybe or-ed with overflow bit. * If overflow occurs, result integer (incorrect) is still returned. * * Don't you dare use this function. */ -unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p) +unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned long long *p, + size_t max_chars) { unsigned long long res; unsigned int rv; res = 0; rv = 0; - while (1) { + while (max_chars--) { unsigned int c = *s; unsigned int lc = c | 0x20; /* don't tolower() this line */ unsigned int val; @@ -82,6 +84,11 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long return rv; } +unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p) +{ + return _parse_integer_limit(s, base, p, INT_MAX); +} + static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res) { unsigned long long _res; diff --git a/lib/kstrtox.h b/lib/kstrtox.h index 3b4637bcd254..158c400ca865 100644 --- a/lib/kstrtox.h +++ b/lib/kstrtox.h @@ -4,6 +4,8 @@ #define KSTRTOX_OVERFLOW (1U << 31) const char *_parse_integer_fixup_radix(const char *s, unsigned int *base); +unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned long long *res, + size_t max_chars); unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *res); #endif diff --git a/lib/vsprintf.c b/lib/vsprintf.c index fb4af73142b4..2766d1b2c301 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -50,6 +50,31 @@ #include #include "kstrtox.h" +static unsigned long long simple_strntoull(const char *startp, size_t max_chars, + char **endp, unsigned int base) +{ + const char *cp; + unsigned long long result = 0ULL; + size_t prefix_chars; + unsigned int rv; + + cp = _parse_integer_fixup_radix(startp, &base); + prefix_chars = cp - startp; + if (prefix_chars < max_chars) { + rv = _parse_integer_limit(cp, base, &result, max_chars - prefix_chars); + /* FIXME */ + cp += (rv & ~KSTRTOX_OVERFLOW); + } else { + /* Field too short for prefix + digit, skip over without converting */ + cp = startp + max_chars; + } + + if (endp) + *endp = (char *)cp; + + return result; +} + /** * simple_strtoull - convert a string to an unsigned long long * @cp: The start of the string @@ -60,18 +85,7 @@ */ unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base) { - unsigned long long result; - unsigned int rv; - - cp = _parse_integer_fixup_radix(cp, &base); - rv = _parse_integer(cp, base, &result); - /* FIXME */ - cp += (rv & ~KSTRTOX_OVERFLOW); - - if (endp) - *endp = (char *)cp; - - return result; + return simple_strntoull(cp, INT_MAX, endp, base); } EXPORT_SYMBOL(simple_strtoull); @@ -106,6 +120,21 @@ long simple_strtol(const char *cp, char **endp, unsigned int base) } EXPORT_SYMBOL(simple_strtol); +static long long simple_strntoll(const char *cp, size_t max_chars, char **endp, + unsigned int base) +{ + /* + * simple_strntoull() safely handles receiving max_chars==0 in the + * case cp[0] == '-' && max_chars == 1. + * If max_chars == 0 we can drop through and pass it to simple_strntoull() + * and the content of *cp is irrelevant. + */ + if (*cp == '-' && max_chars > 0) + return -simple_strntoull(cp + 1, max_chars - 1, endp, base); + + return simple_strntoull(cp, max_chars, endp, base); +} + /** * simple_strtoll - convert a string to a signed long long * @cp: The start of the string @@ -116,10 +145,7 @@ EXPORT_SYMBOL(simple_strtol); */ long long simple_strtoll(const char *cp, char **endp, unsigned int base) { - if (*cp == '-') - return -simple_strtoull(cp + 1, endp, base); - - return simple_strtoull(cp, endp, base); + return simple_strntoll(cp, INT_MAX, endp, base); } EXPORT_SYMBOL(simple_strtoll); @@ -3343,25 +3369,13 @@ int vsscanf(const char *buf, const char *fmt, va_list args) break; if (is_sign) - val.s = qualifier != 'L' ? - simple_strtol(str, &next, base) : - simple_strtoll(str, &next, base); + val.s = simple_strntoll(str, + field_width >= 0 ? field_width : INT_MAX, + &next, base); else - val.u = qualifier != 'L' ? - simple_strtoul(str, &next, base) : - simple_strtoull(str, &next, base); - - if (field_width > 0 && next - str > field_width) { - if (base == 0) - _parse_integer_fixup_radix(str, &base); - while (next - str > field_width) { - if (is_sign) - val.s = div_s64(val.s, base); - else - val.u = div_u64(val.u, base); - --next; - } - } + val.u = simple_strntoull(str, + field_width >= 0 ? field_width : INT_MAX, + &next, base); switch (qualifier) { case 'H': /* that's 'hh' in format */