From patchwork Tue Feb 9 15:56:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Fitzgerald X-Patchwork-Id: 12078501 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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 B5384C43381 for ; Tue, 9 Feb 2021 15:57:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 778F564E99 for ; Tue, 9 Feb 2021 15:57:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232631AbhBIP5k (ORCPT ); Tue, 9 Feb 2021 10:57:40 -0500 Received: from mx0b-001ae601.pphosted.com ([67.231.152.168]:30592 "EHLO mx0b-001ae601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232630AbhBIP5f (ORCPT ); Tue, 9 Feb 2021 10:57:35 -0500 Received: from pps.filterd (m0077474.ppops.net [127.0.0.1]) by mx0b-001ae601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 119Fei2k008424; Tue, 9 Feb 2021 09:56:19 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cirrus.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=PODMain02222019; bh=BYY/FcRwnCXbs+kpJl7of4Go6urKT9Gt+13BQEif+AY=; b=qd8eIIB0dBm/RlgYBIVDNfkwV8d6QFqhIn8f6qRt0QyXKYGvOe3PcWRRbsQX4PQs+29L uHFXLzg1iuXj9SUimGCf4uBB/b8bdpgSzMnK4VGo3W/7/gyqfk+IoOcws+tyxkDnGZjo e4a5ZzyNNc65LbK/UEkDdpFtoDq8dCbVsxFIcQk7Y4QaPFlqlRM/Uf+dIl1rO2wjSw/M gwsUuQWlU8BdIyyTv0OU905WOaSOKfmDtDoNZ5OXZ7g8vamNuHjEGsrUxjoAiyLCDI+T JfrtkDyKXrhY6XOjho42NmDtd7SGc1642JdY8vQfeZifck8WUqVWeDJtUJMSD382J+LM tg== Received: from ediex02.ad.cirrus.com ([87.246.76.36]) by mx0b-001ae601.pphosted.com with ESMTP id 36hrv2c1ap-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Tue, 09 Feb 2021 09:56:18 -0600 Received: from EDIEX01.ad.cirrus.com (198.61.84.80) by EDIEX02.ad.cirrus.com (198.61.84.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Tue, 9 Feb 2021 15:56:17 +0000 Received: from ediswmail.ad.cirrus.com (198.61.86.93) by EDIEX01.ad.cirrus.com (198.61.84.80) with Microsoft SMTP Server id 15.1.1913.5 via Frontend Transport; Tue, 9 Feb 2021 15:56:17 +0000 Received: from AUSNPC0LSNW1-debian.cirrus.com (AUSNPC0LSNW1.ad.cirrus.com [198.61.64.240]) by ediswmail.ad.cirrus.com (Postfix) with ESMTP id 8A31C2AB; Tue, 9 Feb 2021 15:56:10 +0000 (UTC) From: Richard Fitzgerald To: , , , , , CC: , , , Richard Fitzgerald Subject: [PATCH v6 2/4] lib: vsprintf: Fix handling of number field widths in vsscanf Date: Tue, 9 Feb 2021 15:56:02 +0000 Message-ID: <20210209155604.6998-2-rf@opensource.cirrus.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210209155604.6998-1-rf@opensource.cirrus.com> References: <20210209155604.6998-1-rf@opensource.cirrus.com> MIME-Version: 1.0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 suspectscore=0 impostorscore=0 clxscore=1015 bulkscore=0 adultscore=0 malwarescore=0 spamscore=0 phishscore=0 priorityscore=1501 mlxscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102090081 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org 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 --- Changed since v5: - Use INT_MAX to mean "unlimited length". - Rework simple_strntoull() to avoid the goto - Rewrite the comment in simple_strntoll() - In vsscanf() change the calls to simple_strnto[u]ll() so that a field_width of 0 is not treated as unlimited. Changed since v3: - Use INT_MAX to mean "unlimited length". - Use while-loop instead of for-loop in _parse_integer_limit(). - Keep the existing arguments for _parse_integer() on their original line. And the corresponding arguments to _parse_integer_limit() formatted/wrapped the same way as _parse_integer(). - Remove redundant check for (max_chars == 0) in simple_strntoull(). - Fixed "vsscanf" -> "vsscanf()" in commit message. --- lib/kstrtox.c | 13 ++++++-- lib/kstrtox.h | 2 ++ lib/vsprintf.c | 88 +++++++++++++++++++++++++++++--------------------- 3 files changed, 63 insertions(+), 40 deletions(-) diff --git a/lib/kstrtox.c b/lib/kstrtox.c index a118b0b1e9b2..0b5fe8b41173 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 28bb26cd1f67..794ecc373bf9 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -53,29 +53,43 @@ #include #include "kstrtox.h" -/** - * simple_strtoull - convert a string to an unsigned long long - * @cp: The start of the string - * @endp: A pointer to the end of the parsed string will be placed here - * @base: The number base to use - * - * This function has caveats. Please use kstrtoull instead. - */ -unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base) +static unsigned long long simple_strntoull(const char *startp, size_t max_chars, + char **endp, unsigned int base) { - unsigned long long result; + const char *cp; + unsigned long long result = 0ULL; + size_t prefix_chars; unsigned int rv; - cp = _parse_integer_fixup_radix(cp, &base); - rv = _parse_integer(cp, base, &result); - /* FIXME */ - cp += (rv & ~KSTRTOX_OVERFLOW); + 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 + * @endp: A pointer to the end of the parsed string will be placed here + * @base: The number base to use + * + * This function has caveats. Please use kstrtoull instead. + */ +unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base) +{ + return simple_strntoull(cp, INT_MAX, endp, base); +} EXPORT_SYMBOL(simple_strtoull); /** @@ -88,7 +102,7 @@ EXPORT_SYMBOL(simple_strtoull); */ unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base) { - return simple_strtoull(cp, endp, base); + return simple_strntoull(cp, INT_MAX, endp, base); } EXPORT_SYMBOL(simple_strtoul); @@ -109,6 +123,21 @@ 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 @@ -119,10 +148,7 @@ 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); @@ -3449,25 +3475,13 @@ 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 */