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From 5dc50c6bca059a9cda6677b1fd0187df1de78ed7 Mon Sep 17 00:00:00 2001
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From: jmaloy <jmaloy@redhat.com>
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Date: Thu, 13 Feb 2020 15:50:48 +0000
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Subject: [PATCH 2/7] util: add slirp_fmt() helpers
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: jmaloy <jmaloy@redhat.com>
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Message-id: <20200213155049.3936-2-jmaloy@redhat.com>
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Patchwork-id: 93824
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O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH 1/2] util: add slirp_fmt() helpers
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Bugzilla: 1798994
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RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Marc-André Lureau <marcandre.lureau@redhat.com>
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Various calls to snprintf() in libslirp assume that snprintf() returns
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"only" the number of bytes written (excluding terminating NUL).
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https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html#tag_16_159_04
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"Upon successful completion, the snprintf() function shall return the
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number of bytes that would be written to s had n been sufficiently
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large excluding the terminating null byte."
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Introduce slirp_fmt() that handles several pathological cases the
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way libslirp usually expect:
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- treat error as fatal (instead of silently returning -1)
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- fmt0() will always \0 end
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- return the number of bytes actually written (instead of what would
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have been written, which would usually result in OOB later), including
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the ending \0 for fmt0()
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- warn if truncation happened (instead of ignoring)
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Other less common cases can still be handled with strcpy/snprintf() etc.
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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Message-Id: <20200127092414.169796-2-marcandre.lureau@redhat.com>
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(cherry picked from libslirp commit 30648c03b27fb8d9611b723184216cd3174b6775)
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Signed-off-by: Jon Maloy <jmaloy@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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slirp/src/util.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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slirp/src/util.h | 3 +++
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2 files changed, 65 insertions(+)
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diff --git a/slirp/src/util.c b/slirp/src/util.c
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index e596087..e3b6257 100644
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--- a/slirp/src/util.c
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+++ b/slirp/src/util.c
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@@ -364,3 +364,65 @@ void slirp_pstrcpy(char *buf, int buf_size, const char *str)
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}
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*q = '\0';
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}
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+
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+static int slirp_vsnprintf(char *str, size_t size,
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+ const char *format, va_list args)
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+{
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+ int rv = vsnprintf(str, size, format, args);
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+
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+ if (rv < 0) {
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+ g_error("vsnprintf() failed: %s", g_strerror(errno));
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+ }
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+
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+ return rv;
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+}
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+
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+/*
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+ * A snprintf()-like function that:
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+ * - returns the number of bytes written (excluding optional \0-ending)
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+ * - dies on error
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+ * - warn on truncation
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+ */
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+int slirp_fmt(char *str, size_t size, const char *format, ...)
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+{
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+ va_list args;
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+ int rv;
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+
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+ va_start(args, format);
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+ rv = slirp_vsnprintf(str, size, format, args);
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+ va_end(args);
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+
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+ if (rv > size) {
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+ g_critical("vsnprintf() truncation");
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+ }
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+
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+ return MIN(rv, size);
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+}
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+
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+/*
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+ * A snprintf()-like function that:
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+ * - always \0-end (unless size == 0)
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+ * - returns the number of bytes actually written, including \0 ending
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+ * - dies on error
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+ * - warn on truncation
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+ */
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+int slirp_fmt0(char *str, size_t size, const char *format, ...)
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+{
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+ va_list args;
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+ int rv;
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+
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+ va_start(args, format);
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+ rv = slirp_vsnprintf(str, size, format, args);
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+ va_end(args);
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+
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+ if (rv >= size) {
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+ g_critical("vsnprintf() truncation");
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+ if (size > 0)
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+ str[size - 1] = '\0';
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+ rv = size;
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+ } else {
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+ rv += 1; /* include \0 */
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+ }
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+
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+ return rv;
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+}
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diff --git a/slirp/src/util.h b/slirp/src/util.h
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index 3c6223c..0558dfc 100644
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--- a/slirp/src/util.h
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+++ b/slirp/src/util.h
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@@ -177,4 +177,7 @@ static inline int slirp_socket_set_fast_reuse(int fd)
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void slirp_pstrcpy(char *buf, int buf_size, const char *str);
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+int slirp_fmt(char *str, size_t size, const char *format, ...);
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+int slirp_fmt0(char *str, size_t size, const char *format, ...);
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+
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#endif
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--
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1.8.3.1
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