From 2a4ee2d1702febccc0d81c1724eb61cb654ed72f Mon Sep 17 00:00:00 2001

From: jmaloy <jmaloy@redhat.com>

Date: Thu, 14 May 2020 21:13:09 +0100

Subject: [PATCH 1/6] util: add slirp_fmt() helpers

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RH-Author: jmaloy <jmaloy@redhat.com>

Message-id: <20200514211314.1534001-2-jmaloy@redhat.com>

Patchwork-id: 96585

O-Subject: [RHEL-8.2.0 qemu-kvm PATCH v2 1/6] util: add slirp_fmt() helpers

Bugzilla: 1834477

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

RH-Acked-by: Kevin Wolf <kwolf@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)

Manual cherry pick, since there is no util.c file in this code version.

Instead, we add the new functions to the file misc.c.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 slirp/misc.c  | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 slirp/slirp.h |  2 ++

 2 files changed, 64 insertions(+)

diff --git a/slirp/misc.c b/slirp/misc.c

index 260187b..035b9ab 100644

--- a/slirp/misc.c

+++ b/slirp/misc.c

@@ -293,3 +293,65 @@ void slirp_connection_info(Slirp *slirp, Monitor *mon)

                        so->so_rcv.sb_cc, so->so_snd.sb_cc);

     }

 }

+

+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/slirp.h b/slirp/slirp.h

index 06febfc..49b8c2c 100644

--- a/slirp/slirp.h

+++ b/slirp/slirp.h

@@ -292,5 +292,7 @@ uint8_t tcp_tos(struct socket *);

 int tcp_emu(struct socket *, struct mbuf *);

 int tcp_ctl(struct socket *);

 struct tcpcb *tcp_drop(struct tcpcb *tp, int err);

+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