Re: [PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
On Mon, Mar 8, 2021 at 11:43 AM David Ahern wrote: > > On 3/8/21 9:26 AM, Balazs Nemeth wrote: > > On Mon, 2021-03-08 at 09:17 -0700, David Ahern wrote: > >> 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. On second thought, since mpls_gso_segment pulls all these headers, it is correct to require it to be a multiple of MPLS_HLEN.
Re: [PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
On 3/8/21 9:26 AM, Balazs Nemeth wrote: > On Mon, 2021-03-08 at 09:17 -0700, David Ahern wrote: >> 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. >> > > What about sizeof(struct mpls_label), like in net/ipv4/tunnel4.c? > I was thinking MPLS_HLEN because of its consistent use with skb manipulations. net/mpls code uses mpls_shim_hdr over mpls_label. Looks like the MPLS code could use some cleanups to make this consistent.
Re: [PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
On Mon, 2021-03-08 at 09:17 -0700, David Ahern wrote: > 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. > What about sizeof(struct mpls_label), like in net/ipv4/tunnel4.c?
Re: [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.
Re: [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 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 > --- > 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.
[PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
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 --- 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; /* Setup inner SKB. */ -- 2.29.2
