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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>
This commit is contained in:
Luiz Capitulino 2013-07-11 14:26:56 -04:00
parent 6453a3a694
commit 8f91ad8a1b
1 changed files with 10 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
scripts/qapi-commands.py
View File

@ -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);
}
''',