On 6/27/17, 10:47 AM, "Joe Stringer" <[email protected]> wrote:
On 27 June 2017 at 10:42, Darrell Ball <[email protected]> wrote:
>
>
> On 6/27/17, 10:40 AM, "Joe Stringer" <[email protected]> wrote:
>
> On 26 June 2017 at 18:19, Darrell Ball <[email protected]> wrote:
> >
> >
> > On 6/26/17, 4:49 PM, "Joe Stringer" <[email protected]> wrote:
> >
> > On 26 June 2017 at 13:22, Joe Stringer <[email protected]> wrote:
> > > On 26 June 2017 at 11:45, Darrell Ball <[email protected]>
wrote:
> > >> On 6/26/17, 10:22 AM, "Joe Stringer" <[email protected]> wrote:
> > >> On 23 June 2017 at 18:57, Darrell Ball
<[email protected]> wrote:
> > >> > On 6/23/17, 4:08 PM, "[email protected]
on behalf of Joe Stringer" <[email protected] on behalf of
[email protected]> wrote:
> > >> > On 17 June 2017 at 15:53, Darrell Ball
<[email protected]> wrote:
> > >> > > @@ -554,34 +681,50 @@ conn_not_found(struct
conntrack *ct, struct dp_packet *pkt,
> > >> > > nc->rev_key = nc->key;
> > >> > > conn_key_reverse(&nc->rev_key);
> > >> > >
> > >> > > + if (helper) {
> > >> > > + nc->alg = xstrdup(helper);
> > >> > > + }
> > >> > > +
> > >> > > + if (alg_exp) {
> > >> > > + nc->alg_related = true;
> > >> > > + nc->mark = alg_exp->master_mark;
> > >> > > + nc->label = alg_exp->master_label;
> > >> > > + nc->master_key =
alg_exp->master_key;
> > >> > > + }
> > >> > > +
> > >> > > if (nat_action_info) {
> > >> > > nc->nat_info =
xmemdup(nat_action_info, sizeof *nc->nat_info);
> > >> > > -
ct_rwlock_wrlock(&ct->nat_resources_lock);
> > >> > > -
> > >> > > - bool nat_res =
nat_select_range_tuple(ct, nc,
> > >> > > -
conn_for_un_nat_copy);
> > >> > >
> > >> > > - if (!nat_res) {
> > >> > > - free(nc->nat_info);
> > >> > > - nc->nat_info = NULL;
> > >> > > - free (nc);
> > >> > > -
ct_rwlock_unlock(&ct->nat_resources_lock);
> > >> > > - return NULL;
> > >> > > - }
> > >> > > + if (alg_exp) {
> > >> > > + nc->rev_key.src.addr =
alg_nat_repl_addr;
> > >> > > + nc->nat_info->nat_action =
NAT_ACTION_DST;
> > >> > > + *conn_for_un_nat_copy = *nc;
> > >> > > + } else {
> > >> > > +
ct_rwlock_wrlock(&ct->resources_lock);
> > >> > > + bool nat_res =
nat_select_range_tuple(
> > >> > > + ct, nc,
conn_for_un_nat_copy);
> > >> > > +
> > >> > > + if (!nat_res) {
> > >> > > + free(nc->nat_info);
> > >> > > + nc->nat_info = NULL;
> > >> > > + free (nc);
> > >> >
> > >> > I think that nc->alg may be leaked here? any
reason it doesn't use
> > >> > delete_conn()?
> > >> >
> > >> > Good
> > >> > Yes, alg will leak in this rare error case and yes,
delete_conn() should be used
> > >> > here, as everywhere.
> > >>
> > >> OK.
> > >>
> > >> > > +
ct_rwlock_unlock(&ct->resources_lock);
> > >> > > + return NULL;
> > >> > > + }
> > >> > >
> > >> > > - if (conn_for_un_nat_copy &&
> > >> > > - nc->conn_type ==
CT_CONN_TYPE_DEFAULT) {
> > >> > > *nc = *conn_for_un_nat_copy;
> > >> >
> > >> > Perhaps nc->alg and/or nc->nat_info may be leaked
here?
> > >> >
> > >> > No, the un_nat conn has no such allocations, so there
is nothing to leak.
> > >>
> > >> I don't mean conn_for_un_nat_copy, I mean *nc which
could have had an
> > >> xstrdup()'d 'alg' attached. Won't this overwrite all
fields in 'nc'?
> > >>
> > >> I see your question now.
> > >> No, at this point, the copy gets the same pointers to the
alg string and nat_info.
> > >> Only nc needs them and the un_nat copy ptrs are nulled.
> > >> There is only one allocation set.
> > >
> > > Hmm. Maybe I'm just missing something, let me walk through it
step by
> > > step below and let's see where it goes.
> > >
> > > if (helper) {
> > > nc->alg = xstrdup(helper);
> > > ^ nc->alg is set
> > > }
> > >
> > > if (alg_exp) {
> > > ^ false; do not execute this block
> > > nc->alg_related = true;
> > > nc->mark = alg_exp->master_mark;
> > > nc->label = alg_exp->master_label;
> > > nc->master_key = alg_exp->master_key;
> > > }
> > >
> > > if (nat_action_info) {
> > > ^ true, execute this part
> > > nc->nat_info = xmemdup(nat_action_info, sizeof
*nc->nat_info);
> > >
> > > if (alg_exp) {
> > > ^ false; skip to else
> > > nc->rev_key.src.addr = alg_nat_repl_addr;
> > > nc->nat_info->nat_action = NAT_ACTION_DST;
> > > *conn_for_un_nat_copy = *nc;
> > > } else {
> > > ^ We go through this condition
> > > ct_rwlock_wrlock(&ct->resources_lock);
> > > bool nat_res = nat_select_range_tuple(
> > > ct, nc,
conn_for_un_nat_copy);
> > >
> > > if (!nat_res) {
> > > ^ false; do not execute this block
> > > free(nc->nat_info);
> > > nc->nat_info = NULL;
> > > free (nc);
> > > ct_rwlock_unlock(&ct->resources_lock);
> > > return NULL;
> > > }
> > >
> > > *nc = *conn_for_un_nat_copy;
> > > ^ Now:
> > > nc->alg is overwritten by conn_for_un_nat_copy->alg
> > > nc->nat_info is overwritten by conn_for_un_nat_copy->nat_info
> > >
> > > We don't free either of these.
> >
> > As discussed offline, the copy of '*nc' into
'*conn_for_un_nat_copy'
> > nested inside nat_select_range_tuple() is very well hidden.
This means
> > that the above is not a problem... but what if (!nat_res) ? Then
> > conn_for_un_nat_copy() has a reference to these alg/nat_info
> > parameters which are freed from 'nc' inside that block, then
> > 'conn_for_un_nat_copy' is returned. Could there be a
use-after-free
> > then?
> >
> > Nope, because there is no un_nat conn.
>
> So you mean that dangling references are returned inside
> conn_for_un_nat_copy but they're just not used?
>
> JTBC, nothing can be used, since there is not even a connection.
So if nat_select_range_tuple() is called, and it runs the "*nat_conn =
*conn;" line which updates conn_for_un_nat_copy, then
nat_select_range_tuple() fails to select a tuple and returns false,
then the if (!nat_res) cleanup / return NULL path is called, then what
cleans up the dangling pointers that are now in conn_for_un_nat_copy?
conn_for_un_nat_copy is a local variable in the caller
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