Messages in this thread | | | Date | Thu, 9 Sep 2021 10:10:05 +0100 | From | Tom Parkin <> | Subject | Re: [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core |
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On Thu, Sep 09, 2021 at 10:01:56 +0100, Tom Parkin wrote: > On Thu, Sep 09, 2021 at 12:32:00 +0800, Xiyu Yang wrote: > > The reference count leak issue may take place in an error handling > > path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the > > return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function > > would directly jump to label invalid, without decrementing the reference > > count of the l2tp_session object session increased earlier by > > l2tp_tunnel_get_session(). This may result in refcount leaks. > > I agree with your analysis. Thanks for catching this! >
Also: I forgot to mention I think this fixes:
4522a70db7aa ("l2tp: fix reading optional fields of L2TPv3")
> > > > Fix this issue by decrease the reference count before jumping to the > > label invalid. > > > > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn> > > Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn> > > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com> > > --- > > net/l2tp/l2tp_core.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c > > index 53486b162f01..93271a2632b8 100644 > > --- a/net/l2tp/l2tp_core.c > > +++ b/net/l2tp/l2tp_core.c > > @@ -869,8 +869,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb) > > } > > > > if (tunnel->version == L2TP_HDR_VER_3 && > > - l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) > > + l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) { > > + l2tp_session_dec_refcount(session); > > goto invalid; > > + } > > The error paths in l2tp_udp_recv_core are a bit convoluted because of > the check (!session || !session->recv_skb) which may or may not need > to drop a session reference if triggered. > > I think it could be simplified since session->recv_skb is always set > for all the current session types in the tree, but doing that is probably > a little patch series on its own. > > > > > l2tp_recv_common(session, skb, ptr, optr, hdrflags, length); > > l2tp_session_dec_refcount(session); > > -- > > 2.7.4 > > > > -- > Tom Parkin > Katalix Systems Ltd > https://katalix.com > Catalysts for your Embedded Linux software development
-- Tom Parkin Katalix Systems Ltd https://katalix.com Catalysts for your Embedded Linux software development [unhandled content-type:application/pgp-signature] | |