[glib/mcatanzaro/glib-2-68-rhel9: 24/27] gutils: Avoid segfault in g_get_user_database_entry

[Michael Catanzaro <mcatanzaro src gnome org>]

commit ffc00caa7391e602fd1ee18f2b1522b313942b05
Author: Jamie Bainbridge <jamie bainbridge gmail com>
Date:   Wed Sep 8 12:08:17 2021 +1000

    gutils: Avoid segfault in g_get_user_database_entry
    
    g_get_user_database_entry() uses variable pwd to store the contents of
    the call to getpwnam_r(), then capitalises the first letter of pw_name
    with g_ascii_toupper (pw->pw_name[0]).
    
    However, as per the getpwnam manpage, the result of that call "may point
    to a static area". When this happens, GLib is trying to edit static
    memory which belongs to a shared library, so segfaults.
    
    Instead, copy pw_name off to a temporary variable, set uppercase on
    that variable, and use the variable to join into the desired string.
    Free the new variable after it is no longer needed.
    
    Signed-off-by: Jamie Bainbridge <jamie bainbridge gmail com>

 glib/gutils.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/glib/gutils.c b/glib/gutils.c
index dad162528..7503c09ea 100644
--- a/glib/gutils.c
+++ b/glib/gutils.c
@@ -685,14 +685,17 @@ g_get_user_database_entry (void)
               {
                 gchar **gecos_fields;
                 gchar **name_parts;
+                gchar *uppercase_pw_name;
 
                 /* split the gecos field and substitute '&' */
                 gecos_fields = g_strsplit (pw->pw_gecos, ",", 0);
                 name_parts = g_strsplit (gecos_fields[0], "&", 0);
-                pw->pw_name[0] = g_ascii_toupper (pw->pw_name[0]);
-                e.real_name = g_strjoinv (pw->pw_name, name_parts);
+                uppercase_pw_name = g_strdup (pw->pw_name);
+                uppercase_pw_name[0] = g_ascii_toupper (uppercase_pw_name[0]);
+                e.real_name = g_strjoinv (uppercase_pw_name, name_parts);
                 g_strfreev (gecos_fields);
                 g_strfreev (name_parts);
+                g_free (uppercase_pw_name);
               }
 #endif