From 8f91ad8a1b4702966d91ea58cd90bbde1faea1b3 Mon Sep 17 00:00:00 2001
From: Luiz Capitulino <lcapitulino@redhat.com>
Date: Thu, 11 Jul 2013 14:26:56 -0400
Subject: [PATCH] qapi: qapi-commands: fix possible leaks on visitor dealloc

In qmp-marshal.c the dealloc visitor calls use the same errp
pointer of the input visitor calls. This means that if any of
the input visitor calls fails, then the dealloc visitor will
return early, before freeing the object's memory.

Here's an example, consider this code:

int qmp_marshal_input_block_passwd(Monitor *mon, const QDict *qdict, QObject **ret)
{
	[...]

    char * device = NULL;
    char * password = NULL;

    mi = qmp_input_visitor_new_strict(QOBJECT(args));
    v = qmp_input_get_visitor(mi);
    visit_type_str(v, &device, "device", errp);
    visit_type_str(v, &password, "password", errp);
    qmp_input_visitor_cleanup(mi);

    if (error_is_set(errp)) {
        goto out;
    }
    qmp_block_passwd(device, password, errp);

out:
    md = qapi_dealloc_visitor_new();
    v = qapi_dealloc_get_visitor(md);
    visit_type_str(v, &device, "device", errp);
    visit_type_str(v, &password, "password", errp);
    qapi_dealloc_visitor_cleanup(md);

	[...]

    return 0;
}

Consider errp != NULL when the out label is reached, we're going
to leak device and password.

This patch fixes this by always passing errp=NULL for dealloc
visitors, meaning that we always try to free them regardless of
any previous failure. The above example would then be:

out:
    md = qapi_dealloc_visitor_new();
    v = qapi_dealloc_get_visitor(md);
    visit_type_str(v, &device, "device", NULL);
    visit_type_str(v, &password, "password", NULL);
    qapi_dealloc_visitor_cleanup(md);

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 scripts/qapi-commands.py | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index e06332bd55..b12b6964ef 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -128,12 +128,15 @@ def gen_visitor_input_vars_decl(args):
 
 def gen_visitor_input_block(args, obj, dealloc=False):
     ret = ""
+    errparg = 'errp'
+
     if len(args) == 0:
         return ret
 
     push_indent()
 
     if dealloc:
+        errparg = 'NULL'
         ret += mcgen('''
 md = qapi_dealloc_visitor_new();
 v = qapi_dealloc_get_visitor(md);
@@ -148,22 +151,22 @@ def gen_visitor_input_block(args, obj, dealloc=False):
     for argname, argtype, optional, structured in parse_args(args):
         if optional:
             ret += mcgen('''
-visit_start_optional(v, &has_%(c_name)s, "%(name)s", errp);
+visit_start_optional(v, &has_%(c_name)s, "%(name)s", %(errp)s);
 if (has_%(c_name)s) {
 ''',
-                         c_name=c_var(argname), name=argname)
+                         c_name=c_var(argname), name=argname, errp=errparg)
             push_indent()
         ret += mcgen('''
-%(visitor)s(v, &%(c_name)s, "%(name)s", errp);
+%(visitor)s(v, &%(c_name)s, "%(name)s", %(errp)s);
 ''',
                      c_name=c_var(argname), name=argname, argtype=argtype,
-                     visitor=type_visitor(argtype))
+                     visitor=type_visitor(argtype), errp=errparg)
         if optional:
             pop_indent()
             ret += mcgen('''
 }
-visit_end_optional(v, errp);
-''')
+visit_end_optional(v, %(errp)s);
+''', errp=errparg)
 
     if dealloc:
         ret += mcgen('''
@@ -194,7 +197,7 @@ def gen_marshal_output(name, args, ret_type, middle_mode):
     }
     qmp_output_visitor_cleanup(mo);
     v = qapi_dealloc_get_visitor(md);
-    %(visitor)s(v, &ret_in, "unused", errp);
+    %(visitor)s(v, &ret_in, "unused", NULL);
     qapi_dealloc_visitor_cleanup(md);
 }
 ''',