Hi Pablo, This issue can be seen in the scenario when there are multiple Contact headers and the first one is using a hostname and other headers use IP addresses. In this case, ct_sip_walk_headers will work the following way: The first ct_sip_get_header call to will find the first Contact header but will return -1 as the header uses a hostname. But matchoff will be changed to the offset of this header. After that, dataoff should be set to matchoff, so that the next ct_sip_get_header call find the next Contact header. But instead of assigning dataoff to matchoff, it is incremented by it, which is not correct, as matchoff is an absolute value of the offset. So on the next call to the ct_sip_get_header, dataoff will be incorrect, and the next Contact header may not be found at all. Best regards, Igor On Tue, Jun 18, 2019 at 1:25 AM Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > > On Wed, Jun 05, 2019 at 12:32:40PM +0300, Igor Ryzhov wrote: > > ct_sip_next_header and ct_sip_get_header return an absolute > > value of matchoff, not a shift from current dataoff. > > So dataoff should be assigned matchoff, not incremented by it. > > Could we get a more detailed description of this bug? A description of > the simplified scenario / situation that help you found it would help > here. > > Thanks. > > > Signed-off-by: Igor Ryzhov <iryzhov@xxxxxxxxxx> > > --- > > net/netfilter/nf_conntrack_sip.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c > > index c30c883c370b..966c5948f926 100644 > > --- a/net/netfilter/nf_conntrack_sip.c > > +++ b/net/netfilter/nf_conntrack_sip.c > > @@ -480,7 +480,7 @@ static int ct_sip_walk_headers(const struct nf_conn *ct, const char *dptr, > > return ret; > > if (ret == 0) > > break; > > - dataoff += *matchoff; > > + dataoff = *matchoff; > > } > > *in_header = 0; > > } > > @@ -492,7 +492,7 @@ static int ct_sip_walk_headers(const struct nf_conn *ct, const char *dptr, > > break; > > if (ret == 0) > > return ret; > > - dataoff += *matchoff; > > + dataoff = *matchoff; > > } > > > > if (in_header) > > -- > > 2.21.0 > >
