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b=XCgw+aiMYtjB84bt6EC3wc5P2d1CBZM27lAcVpwvVnIdPKXIUDmxpwkpOpPvJgMjU z8YyEkxjP+KgWynJZrfmHnkLGkM3HRGozNvNmIGiRL2w9eajrrc/xU9XSXQTOuMxKl uk7EbWg2bpAdOVWAwso8DalSOrjHPpOs5sZy5he2AcWFVrtKYIlp008it8h85tzeiK g/uirUmElownoNiKUXepy0UugdCJ0vXBTA72x5M003exeqp1LtjT7qdO37l+S2n1nE RjMbTdxnxVVOG18yOEDnnb4bdpNV1wQFfxMJVVB4cKVQ/AHoDWKelVdfziOB21k1CE 15LVNNWguugVg== Date: Fri, 11 Jul 2025 03:56:38 +0200 From: Alejandro Colomar To: linux-mm@kvack.org, linux-hardening@vger.kernel.org Cc: Alejandro Colomar , Kees Cook , Christopher Bazley , shadow <~hallyn/shadow@lists.sr.ht>, linux-kernel@vger.kernel.org, Andrew Morton , kasan-dev@googlegroups.com, Dmitry Vyukov , Alexander Potapenko , Marco Elver , Christoph Lameter , David Rientjes , Vlastimil Babka , Roman Gushchin , Harry Yoo , Andrew Clayton , Rasmus Villemoes , Michal Hocko , Linus Torvalds , Al Viro , Martin Uecker , Sam James , Andrew Pinski Subject: [RFC v6 1/8] vsprintf: Add [v]sprintf_trunc() Message-ID: X-Mailer: git-send-email 2.50.0 References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: CB5B5C000F X-Rspamd-Server: rspam09 X-Stat-Signature: gzd6q4oahekt6bq9iibfw73iocg6z1ec X-HE-Tag: 1752199005-977422 X-HE-Meta: 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 TLdGxfKG 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: sprintf_trunc() is a function similar to strscpy(). It truncates the string, and returns an error code on truncation or error. On success, it returns the length of the new string. Cc: Kees Cook Cc: Christopher Bazley Cc: Rasmus Villemoes Cc: Marco Elver Cc: Michal Hocko Cc: Linus Torvalds Cc: Al Viro Signed-off-by: Alejandro Colomar --- include/linux/sprintf.h | 2 ++ lib/vsprintf.c | 53 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 55 insertions(+) diff --git a/include/linux/sprintf.h b/include/linux/sprintf.h index 51cab2def9ec..5ea6ec9c2e59 100644 --- a/include/linux/sprintf.h +++ b/include/linux/sprintf.h @@ -13,6 +13,8 @@ __printf(3, 4) int snprintf(char *buf, size_t size, const char *fmt, ...); __printf(3, 0) int vsnprintf(char *buf, size_t size, const char *fmt, va_list args); __printf(3, 4) int scnprintf(char *buf, size_t size, const char *fmt, ...); __printf(3, 0) int vscnprintf(char *buf, size_t size, const char *fmt, va_list args); +__printf(3, 4) int sprintf_trunc(char *buf, size_t size, const char *fmt, ...); +__printf(3, 0) int vsprintf_trunc(char *buf, size_t size, const char *fmt, va_list args); __printf(2, 3) __malloc char *kasprintf(gfp_t gfp, const char *fmt, ...); __printf(2, 0) __malloc char *kvasprintf(gfp_t gfp, const char *fmt, va_list args); __printf(2, 0) const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list args); diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 01699852f30c..15e780942c56 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2923,6 +2923,34 @@ int vscnprintf(char *buf, size_t size, const char *fmt, va_list args) } EXPORT_SYMBOL(vscnprintf); +/** + * vsprintf_trunc - va_list string truncate print formatted + * @buf: The buffer to place the result into + * @size: The size of the buffer, including the trailing null space + * @fmt: The format string to use + * @args: Arguments for the format string + * + * The return value is the length of the string. + * If the string is truncated, the function returns -E2BIG. + * If @size is invalid, the function returns -EOVERFLOW. + * + * See the vsnprintf() documentation for format string extensions over C99. + */ +int vsprintf_trunc(char *buf, size_t size, const char *fmt, va_list args) +{ + int len; + + if (WARN_ON_ONCE(size == 0 || size > INT_MAX)) + return -EOVERFLOW; + + len = vsnprintf(buf, size, fmt, args); + if (unlikely(len >= size)) + return -E2BIG; + + return len; +} +EXPORT_SYMBOL(vsprintf_trunc); + /** * snprintf - Format a string and place it in a buffer * @buf: The buffer to place the result into @@ -2974,6 +3002,31 @@ int scnprintf(char *buf, size_t size, const char *fmt, ...) } EXPORT_SYMBOL(scnprintf); +/** + * sprintf_trunc - string truncate print formatted + * @buf: The buffer to place the result into + * @size: The size of the buffer, including the trailing null space + * @fmt: The format string to use + * @...: Arguments for the format string + * + * The return value is the length of the string. + * If the string is truncated, the function returns -E2BIG. + * If @size is invalid, the function returns -EOVERFLOW. + */ + +int sprintf_trunc(char *buf, size_t size, const char *fmt, ...) +{ + int len; + va_list args; + + va_start(args, fmt); + len = vsprintf_trunc(buf, size, fmt, args); + va_end(args); + + return len; +} +EXPORT_SYMBOL(sprintf_trunc); + /** * vsprintf - Format a string and place it in a buffer * @buf: The buffer to place the result into -- 2.50.0