[glibc] iconv: Remove alloca use in gconv-modules configuration parsing

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e3217c7fd9e67aa2d53700bb1da9a966e73b9684

commit e3217c7fd9e67aa2d53700bb1da9a966e73b9684
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Thu Jun 10 00:41:35 2021 +0530

    iconv: Remove alloca use in gconv-modules configuration parsing
    
    The alloca sizes ought to be constrained to PATH_MAX, but replace them
    with dynamic allocation to be safe.  A static PATH_MAX array would
    have worked too but Hurd does not have PATH_MAX and the code path is
    not hot enough to micro-optimise this allocation.  Revisit if any of
    those realities change.
    
    Reviewed-by: DJ Delorie <dj@redhat.com>

Diff:
---
 iconv/gconv_conf.c  | 17 +++++++++--------
 iconv/iconvconfig.c | 17 +++++++++++------
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/iconv/gconv_conf.c b/iconv/gconv_conf.c
index c8ad8099a4..3f2cef255b 100644
--- a/iconv/gconv_conf.c
+++ b/iconv/gconv_conf.c
@@ -559,15 +559,15 @@ __gconv_read_conf (void)
 
   for (cnt = 0; __gconv_path_elem[cnt].name != NULL; ++cnt)
     {
-#define BUF_LEN elem_len + sizeof (gconv_conf_dirname)
-
       const char *elem = __gconv_path_elem[cnt].name;
       size_t elem_len = __gconv_path_elem[cnt].len;
-      char *buf;
 
       /* No slash needs to be inserted between elem and gconv_conf_filename;
 	 elem already ends in a slash.  */
-      buf = alloca (BUF_LEN);
+      char *buf = malloc (elem_len + sizeof (gconv_conf_dirname));
+      if (buf == NULL)
+	continue;
+
       char *cp = __mempcpy (__mempcpy (buf, elem, elem_len),
 			    gconv_conf_filename, sizeof (gconv_conf_filename));
 
@@ -596,15 +596,16 @@ __gconv_read_conf (void)
 	      if (len > strlen (suffix)
 		  && strcmp (ent->d_name + len - strlen (suffix), suffix) == 0)
 		{
-		  /* LEN <= PATH_MAX so this alloca is not unbounded.  */
-		  char *conf = alloca (BUF_LEN + len + 1);
-		  cp = stpcpy (conf, buf);
-		  sprintf (cp, "/%s", ent->d_name);
+		  char *conf;
+		  if (__asprintf (&conf, "%s/%s", buf, ent->d_name) < 0)
+		    continue;
 		  read_conf_file (conf, elem, elem_len, &modules, &nmodules);
+		  free (conf);
 		}
 	    }
 	  __closedir (confdir);
 	}
+      free (buf);
     }
 #endif
 
diff --git a/iconv/iconvconfig.c b/iconv/iconvconfig.c
index b2a868919c..c9607fb645 100644
--- a/iconv/iconvconfig.c
+++ b/iconv/iconvconfig.c
@@ -712,7 +712,6 @@ handle_file (const char *dir, const char *infile)
 static int
 handle_dir (const char *dir)
 {
-#define BUF_LEN prefix_len + dirlen + sizeof "gconv-modules.d"
   char *cp;
   size_t dirlen = strlen (dir);
   bool found = false;
@@ -726,7 +725,10 @@ handle_dir (const char *dir)
     }
 
   /* First, look for a gconv-modules file.  */
-  char buf[BUF_LEN];
+  char *buf = malloc (prefix_len + dirlen + sizeof "gconv-modules.d");
+  if (buf == NULL)
+    goto out;
+
   cp = buf;
   if (dir[0] == '/')
     cp = mempcpy (cp, prefix, prefix_len);
@@ -756,16 +758,19 @@ handle_dir (const char *dir)
 	  if (len > strlen (suffix)
 	      && strcmp (ent->d_name + len - strlen (suffix), suffix) == 0)
 	    {
-	      /* LEN <= PATH_MAX so this alloca is not unbounded.  */
-	      char *conf = alloca (BUF_LEN + len + 1);
-	      cp = stpcpy (conf, buf);
-	      sprintf (cp, "/%s", ent->d_name);
+	      char *conf;
+	      if (asprintf (&conf, "%s/%s", buf, ent->d_name) < 0)
+		continue;
 	      found |= handle_file (dir, conf);
+	      free (conf);
 	    }
 	}
       closedir (confdir);
     }
 
+  free (buf);
+
+out:
   if (!found)
     {
       error (0, errno, "failed to open gconv configuration files in `%s'",