Re: [Qemu-devel] [PATCH] hostmem: Validate host-nodes before setting bitmap

[Eduardo Habkost]

On Fri, Nov 30, 2018 at 09:37:49AM +0100, Markus Armbruster wrote:
> Eduardo Habkost <address@hidden> 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 <address@hidden>
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> >  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().

Thanks, I will fix it in v2.


> 
> > 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 <address@hidden>
> > +#
> > +# 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.

If such a test existed, yes.

> 
> Reviewed-by: Markus Armbruster <address@hidden>

Thanks!

(Although this version is broken due to the extra "l = l->next"
line and we need v2)

-- 
Eduardo