From: Markus Armbruster <armbru@redhat.com>
References: <20181129185754.7009-1-ehabkost@redhat.com>
Date: Fri, 30 Nov 2018 09:37:49 +0100
In-Reply-To: <20181129185754.7009-1-ehabkost@redhat.com> (Eduardo Habkost's
	message of "Thu, 29 Nov 2018 16:57:54 -0200")
Message-ID: <874lbzneoy.fsf@dusky.pond.sub.org>
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [Qemu-devel] [PATCH] hostmem: Validate host-nodes before
 setting bitmap
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: qemu-devel@nongnu.org, Igor Mammedov <imammedo@redhat.com>, David Hildenbrand <david@redhat.com>

Eduardo Habkost <ehabkost@redhat.com> writes:

> host_memory_backend_set_host_nodes() was not validating
> host-nodes before writing to backend->host_nodes, making QEMU
> write beyond the end of the bitmap.
>
> Fix the crash and add a simple regression test for the fix.
>
> Reported-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  backends/hostmem.c                   | 13 +++++++---
>  tests/acceptance/host-nodes-limit.py | 36 ++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+), 3 deletions(-)
>  create mode 100644 tests/acceptance/host-nodes-limit.py
>
> diff --git a/backends/hostmem.c b/backends/hostmem.c
> index 1a89342039..ef199d32fd 100644
> --- a/backends/hostmem.c
> +++ b/backends/hostmem.c
> @@ -103,11 +103,18 @@ host_memory_backend_set_host_nodes(Object *obj, Visitor *v, const char *name,
>  {
>  #ifdef CONFIG_NUMA
>      HostMemoryBackend *backend = MEMORY_BACKEND(obj);
> -    uint16List *l = NULL;
> +    uint16List *l, *host_nodes = NULL;
>  
> -    visit_type_uint16List(v, name, &l, errp);
> +    visit_type_uint16List(v, name, &host_nodes, errp);
> +
> +    for (l = host_nodes; l; l = l->next) {
> +        if (l->value >= MAX_NODES) {
> +            error_setg(errp, "Invalid host-nodes value: %d", l->value);
> +            return;
> +        }
> +    }
>  
> -    while (l) {
> +    for (l = host_nodes; l; l = l->next) {
>          bitmap_set(backend->host_nodes, l->value, 1);
>          l = l->next;
>      }

Pre-existing: leaks the list created by visit_type_uint16List(), or am I
confused?

host_memory_backend_set_host_nodes() looks like it leaks, too.  

The function to free such lists is qapi_free_uint16List().

> diff --git a/tests/acceptance/host-nodes-limit.py b/tests/acceptance/host-nodes-limit.py
> new file mode 100644
> index 0000000000..e803e10104
> --- /dev/null
> +++ b/tests/acceptance/host-nodes-limit.py
> @@ -0,0 +1,36 @@
> +# Regression test for host-nodes limit validation
> +#
> +# Copyright (c) 2018 Red Hat, Inc.
> +#
> +# Author:
> +#  Eduardo Habkost <ehabkost@redhat.com>
> +#
> +# This work is licensed under the terms of the GNU GPL, version 2 or
> +# later.  See the COPYING file in the top-level directory.
> +
> +from avocado_qemu import Test
> +from subprocess import Popen, PIPE
> +
> +MAX_NODES = 128
> +
> +class HostNodesValidation(Test):
> +    def test_large_host_nodes(self):
> +        p = Popen([self.qemu_bin, '-display', 'none', '-nodefaults',
> +                   '-object', 'memory-backend-ram,id=m0,'
> +                              'size=4096,host-nodes=%d' % (MAX_NODES)],
> +                  stderr=PIPE, stdout=PIPE)
> +        stdout,stderr = p.communicate()
> +
> +        self.assertIn(b'Invalid host-nodes', stderr)
> +        self.assertEquals(stdout, b'')
> +        self.assertEquals(p.returncode, 1)
> +
> +    def test_valid_host_nodes(self):
> +        p = Popen([self.qemu_bin, '-display', 'none', '-nodefaults',
> +                   '-object', 'memory-backend-ram,id=m0,'
> +                              'size=4096,host-nodes=%d' % (MAX_NODES - 1)],
> +                  stderr=PIPE, stdout=PIPE)
> +        stdout,stderr = p.communicate()
> +
> +        self.assertIn(b'host-nodes must be empty', stderr)
> +        self.assertEquals(p.returncode, 1)

Perhaps this test should become part of a more comprehensive
menory-backend-ram test.

Reviewed-by: Markus Armbruster <armbru@redhat.com>