From: Maria Matejka <mq@ucw.cz>
Date: Wed, 10 Jul 2019 09:12:41 +0000 (+0200)
Subject: Debug: growing message format buffer
X-Git-Tag: v1.6.7~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=46faedff2990ca3e065931b36ab2133b3633bd25;p=thirdparty%2Fbird.git

Debug: growing message format buffer

This led in corner cases to undefined buffer content
and garbage output.
---

diff --git a/sysdep/unix/log.c b/sysdep/unix/log.c
index 08623d01d..22291dc1e 100644
--- a/sysdep/unix/log.c
+++ b/sysdep/unix/log.c
@@ -242,14 +242,23 @@ die(const char *msg, ...)
 void
 debug(const char *msg, ...)
 {
+#define MAX_DEBUG_BUFSIZE       65536
   va_list args;
-  char buf[1024];
+  static uint bufsize = 4096;
+  static char *buf = NULL;
+
+  if (!buf)
+    buf = mb_alloc(&root_pool, bufsize);
 
   va_start(args, msg);
   if (dbgf)
     {
-      if (bvsnprintf(buf, sizeof(buf), msg, args) < 0)
-	bsprintf(buf + sizeof(buf) - 100, " ... <too long>\n");
+      while (bvsnprintf(buf, bufsize, msg, args) < 0)
+        if (bufsize >= MAX_DEBUG_BUFSIZE)
+          bug("Extremely long debug output, split it.");
+        else
+          buf = mb_realloc(buf, (bufsize *= 2));
+
       fputs(buf, dbgf);
     }
   va_end(args);