From 5dc50c6bca059a9cda6677b1fd0187df1de78ed7 Mon Sep 17 00:00:00 2001 From: jmaloy Date: Thu, 13 Feb 2020 15:50:48 +0000 Subject: [PATCH 2/7] util: add slirp_fmt() helpers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: jmaloy Message-id: <20200213155049.3936-2-jmaloy@redhat.com> Patchwork-id: 93824 O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH 1/2] util: add slirp_fmt() helpers Bugzilla: 1798994 RH-Acked-by: Eduardo Habkost RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Stefan Hajnoczi 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) Signed-off-by: Jon Maloy Signed-off-by: Danilo C. L. de Paula --- slirp/src/util.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ slirp/src/util.h | 3 +++ 2 files changed, 65 insertions(+) diff --git a/slirp/src/util.c b/slirp/src/util.c index e596087..e3b6257 100644 --- a/slirp/src/util.c +++ b/slirp/src/util.c @@ -364,3 +364,65 @@ void slirp_pstrcpy(char *buf, int buf_size, const char *str) } *q = '\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 + */ +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 + */ +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; +} diff --git a/slirp/src/util.h b/slirp/src/util.h index 3c6223c..0558dfc 100644 --- a/slirp/src/util.h +++ b/slirp/src/util.h @@ -177,4 +177,7 @@ static inline int slirp_socket_set_fast_reuse(int fd) void slirp_pstrcpy(char *buf, int buf_size, const char *str); +int slirp_fmt(char *str, size_t size, const char *format, ...); +int slirp_fmt0(char *str, size_t size, const char *format, ...); + #endif -- 1.8.3.1