From 8f130c9462750f2ec8205b0749ecd64b799144b5 Mon Sep 17 00:00:00 2001 From: jmaloy Date: Wed, 19 Feb 2020 16:29:22 +0100 Subject: [PATCH 1/2] util: add slirp_fmt() helpers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Message-id: <20200219162923.18327-2-jmaloy@redhat.com> Patchwork-id: 93976 O-Subject: [RHEL-7.8 qemu-kvm-rhev PATCH v2 1/2] util: add slirp_fmt() helpers Bugzilla: 1798974 RH-Acked-by: Maxim Levitsky RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Eduardo Habkost From: Marc-André Lureau Various calls to snprintf() in libslirp assume that snprintf() returns "only" the number of bytes written (excluding terminating NUL). https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html#tag_16_159_04 "Upon successful completion, the snprintf() function shall return the number of bytes that would be written to s had n been sufficiently large excluding the terminating null byte." Introduce slirp_fmt() that handles several pathological cases the way libslirp usually expect: - treat error as fatal (instead of silently returning -1) - fmt0() will always \0 end - return the number of bytes actually written (instead of what would have been written, which would usually result in OOB later), including the ending \0 for fmt0() - warn if truncation happened (instead of ignoring) Other less common cases can still be handled with strcpy/snprintf() etc. Signed-off-by: Marc-André Lureau Reviewed-by: Samuel Thibault Message-Id: <20200127092414.169796-2-marcandre.lureau@redhat.com> (cherry picked from libslirp commit 30648c03b27fb8d9611b723184216cd3174b6775) Manually re-adapted, since there is no util.c file in this code version. We add the two functions as static functions in the file where they are going to be used. Signed-off-by: Jon Maloy Signed-off-by: Miroslav Rezanina --- slirp/tcp_subr.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c index b95ba23..c5196a4 100644 --- a/slirp/tcp_subr.c +++ b/slirp/tcp_subr.c @@ -45,6 +45,9 @@ /* Don't do rfc1323 performance enhancements */ #define TCP_DO_RFC1323 0 +static int slirp_fmt(char *str, size_t size, const char *format, ...); +static int slirp_fmt0(char *str, size_t size, const char *format, ...); + /* * Tcp initialization */ @@ -990,3 +993,65 @@ int tcp_ctl(struct socket *so) sb->sb_wptr += sb->sb_cc; return 0; } + +static int slirp_vsnprintf(char *str, size_t size, + const char *format, va_list args) +{ + int rv = vsnprintf(str, size, format, args); + + if (rv < 0) { + g_error("vsnprintf() failed: %s", g_strerror(errno)); + } + + return rv; +} + +/* + * A snprintf()-like function that: + * - returns the number of bytes written (excluding optional \0-ending) + * - dies on error + * - warn on truncation + */ +static int slirp_fmt(char *str, size_t size, const char *format, ...) +{ + va_list args; + int rv; + + va_start(args, format); + rv = slirp_vsnprintf(str, size, format, args); + va_end(args); + + if (rv > size) { + g_critical("vsnprintf() truncation"); + } + + return MIN(rv, size); +} + +/* + * A snprintf()-like function that: + * - always \0-end (unless size == 0) + * - returns the number of bytes actually written, including \0 ending + * - dies on error + * - warn on truncation + */ +static int slirp_fmt0(char *str, size_t size, const char *format, ...) +{ + va_list args; + int rv; + + va_start(args, format); + rv = slirp_vsnprintf(str, size, format, args); + va_end(args); + + if (rv >= size) { + g_critical("vsnprintf() truncation"); + if (size > 0) + str[size - 1] = '\0'; + rv = size; + } else { + rv += 1; /* include \0 */ + } + + return rv; +} -- 1.8.3.1