From 8f130c9462750f2ec8205b0749ecd64b799144b5 Mon Sep 17 00:00:00 2001
From: jmaloy <jmaloy@redhat.com>
Date: Wed, 19 Feb 2020 16:29:22 +0100
Subject: [PATCH 1/2] util: add slirp_fmt() helpers
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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 <mlevitsk@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
From: Marc-André Lureau <marcandre.lureau@redhat.com>
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 <marcandre.lureau@redhat.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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 <jmaloy@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
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