Willem de Bruijn
2021-Mar-08 16:07 UTC
[PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
On Mon, Mar 8, 2021 at 5:32 AM Balazs Nemeth <bnemeth at redhat.com> wrote:> > A packet with skb_inner_network_header(skb) == skb_network_header(skb) > and ETH_P_MPLS_UC will prevent mpls_gso_segment from pulling any headers > from the packet. Subsequently, the call to skb_mac_gso_segment will > again call mpls_gso_segment with the same packet leading to an infinite > loop. > > Signed-off-by: Balazs Nemeth <bnemeth at redhat.com> > --- > net/mpls/mpls_gso.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/mpls/mpls_gso.c b/net/mpls/mpls_gso.c > index b1690149b6fa..cc1b6457fc93 100644 > --- a/net/mpls/mpls_gso.c > +++ b/net/mpls/mpls_gso.c > @@ -27,7 +27,7 @@ static struct sk_buff *mpls_gso_segment(struct sk_buff *skb, > > skb_reset_network_header(skb); > mpls_hlen = skb_inner_network_header(skb) - skb_network_header(skb); > - if (unlikely(!pskb_may_pull(skb, mpls_hlen))) > + if (unlikely(!mpls_hlen || !pskb_may_pull(skb, mpls_hlen))) > goto out;Good cathc. Besides length zero, this can be more strict: a label is 4B, so mpls_hlen needs to be >= 4B. Perhaps even aligned to 4B, too, but not if there may be other encap on top. Unfortunately there is no struct or type definition that we can use a sizeof instead of open coding the raw constant.
David Ahern
2021-Mar-08 16:17 UTC
[PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
On 3/8/21 9:07 AM, Willem de Bruijn wrote:>> diff --git a/net/mpls/mpls_gso.c b/net/mpls/mpls_gso.c >> index b1690149b6fa..cc1b6457fc93 100644 >> --- a/net/mpls/mpls_gso.c >> +++ b/net/mpls/mpls_gso.c >> @@ -27,7 +27,7 @@ static struct sk_buff *mpls_gso_segment(struct sk_buff *skb, >> >> skb_reset_network_header(skb); >> mpls_hlen = skb_inner_network_header(skb) - skb_network_header(skb); >> - if (unlikely(!pskb_may_pull(skb, mpls_hlen))) >> + if (unlikely(!mpls_hlen || !pskb_may_pull(skb, mpls_hlen))) >> goto out; > > Good cathc. Besides length zero, this can be more strict: a label is > 4B, so mpls_hlen needs to be >= 4B. > > Perhaps even aligned to 4B, too, but not if there may be other encap on top. > > Unfortunately there is no struct or type definition that we can use a > sizeof instead of open coding the raw constant. >MPLS_HLEN can be used here.