iconvconfig: Fix multiple issues

It was noticed on big-endian systems that msgfmt would fail with the
following error:

msgfmt: gconv_builtin.c:70: __gconv_get_builtin_trans: Assertion `cnt < sizeof (map) / sizeof (map[0])' failed.
Aborted (core dumped)

This is only seen on installed systems because it was due to a
corrupted gconv-modules.cache.  iconvconfig had the following issues
(it was specifically freeing fulldir that caused this issue, but other
cleanups are also needed) that this patch fixes.

- Add prefix only if dir starts with '/'
- Use asprintf instead of mempcpy so that the directory string is NULL
  terminated
- Make a copy of the directory reference in new_module so that fulldir
  can be freed within the same scope in handle_dir.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

2 files changed, 10 insertions, 16 deletions

diff --git a/iconv/Makefile b/iconv/Makefile
index a9b267c851..07d77c9eca 100644
--- a/iconv/Makefile
+++ b/iconv/Makefile
@@ -33,7 +33,7 @@ vpath %.c ../locale/programs ../intl
 iconv_prog-modules = iconv_charmap charmap charmap-dir linereader \
 		     dummy-repertoire simple-hash xstrdup xmalloc \
 		     record-status
-iconvconfig-modules = strtab xmalloc hash-string
+iconvconfig-modules = strtab xmalloc xasprintf xstrdup hash-string
 extra-objs	   = $(iconv_prog-modules:=.o) $(iconvconfig-modules:=.o)
 CFLAGS-iconv_prog.c += -I../locale/programs
 CFLAGS-iconv_charmap.c += -I../locale/programs
diff --git a/iconv/iconvconfig.c b/iconv/iconvconfig.c
index e69334d71c..783b2bbdbb 100644
--- a/iconv/iconvconfig.c
+++ b/iconv/iconvconfig.c
@@ -250,6 +250,7 @@ static const char gconv_module_ext[] = MODULE_EXT;
 
 
 #include <programs/xmalloc.h>
+#include <programs/xasprintf.h>
 
 
 /* C string table handling.  */
@@ -519,11 +520,12 @@ module_compare (const void *p1, const void *p2)
 /* Create new module record.  */
 static void
 new_module (const char *fromname, size_t fromlen, const char *toname,
-	    size_t tolen, const char *directory,
+	    size_t tolen, const char *dir_in,
 	    const char *filename, size_t filelen, int cost, size_t need_ext)
 {
   struct module *new_module;
-  size_t dirlen = strlen (directory) + 1;
+  size_t dirlen = strlen (dir_in) + 1;
+  const char *directory = xstrdup (dir_in);
   char *tmp;
   void **inserted;
 
@@ -654,20 +656,10 @@ handle_dir (const char *dir)
   size_t dirlen = strlen (dir);
   bool found = false;
 
-  /* Add the prefix before sending it off to the parser.  */
-  char *fulldir = xmalloc (prefix_len + dirlen + 2);
-  char *cp = mempcpy (mempcpy (fulldir, prefix, prefix_len), dir, dirlen);
+  char *fulldir = xasprintf ("%s%s%s", dir[0] == '/' ? prefix : "",
+			     dir, dir[dirlen - 1] != '/' ? "/" : "");
 
-  if (dir[dirlen - 1] != '/')
-    {
-      *cp++ = '/';
-      *cp = '\0';
-      dirlen++;
-    }
-
-  found = gconv_parseconfdir (fulldir, dirlen + prefix_len);
-
-  free (fulldir);
+  found = gconv_parseconfdir (fulldir, strlen (fulldir));
 
   if (!found)
     {
@@ -679,6 +671,8 @@ handle_dir (const char *dir)
 	     "configuration files with names ending in .conf.");
     }
 
+  free (fulldir);
+
   return found ? 0 : 1;
 }