| Message ID | 20180619234406.8217-1-michael@opensourcefoundries.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
Hi, On Tue, Jun 19, 2018 at 04:44:06PM -0700, Michael Scott wrote: > After decompression of 6lowpan socket data, an IPv6 header is inserted > before the existing socket payload. After this, we reset the > network_header value of the skb to account for the difference in payload > size from prior to decompression + the addition of the IPv6 header. > > However, we fail to reset the mac_header value. > > Leaving the mac_header value untouched here, can cause a calculation > error in net/packet/af_packet.c packet_rcv() function when an > AF_PACKET socket is opened in SOCK_RAW mode for use on a 6lowpan > interface. > > On line 2088, the data pointer is moved backward by the value returned > from skb_mac_header(). If skb->data is adjusted so that it is before > the skb->head pointer (which can happen when an old value of mac_header > is left in place) the kernel generates a panic in net/core/skbuff.c > line 1717. > > This panic can be generated by BLE 6lowpan interfaces (such as bt0) and > 802.15.4 interfaces (such as lowpan0) as they both use the same 6lowpan > sources for compression and decompression. > > Signed-off-by: Michael Scott <michael@opensourcefoundries.com> > --- > net/6lowpan/iphc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c > index 6b1042e21656..52fad5dad9f7 100644 > --- a/net/6lowpan/iphc.c > +++ b/net/6lowpan/iphc.c > @@ -770,6 +770,7 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev, > hdr.hop_limit, &hdr.daddr); > > skb_push(skb, sizeof(hdr)); > + skb_reset_mac_header(skb); > skb_reset_network_header(skb); > skb_copy_to_linear_data(skb, &hdr, sizeof(hdr)); > I think it's good to make that if the mac_header gets a dangled pointer. But we don't have a mac header at this point anymore... There exists also some functionality that the MAC header is not set, I suppose this can be usefuly for tun like interfaces e.g. RAW IP what we have here. skb_mac_header_was_set which does: return skb->mac_header != (typeof(skb->mac_header))~0U; maybe we can set it as (typeof(skb->mac_header))~0U and then everything will run as far the kernel will not crash anymore. Question is for me: which upper layer wants access MAC header here on receive path? It cannot parsed anyhow because so far I know no upper layer can parse at the moment 802.15.4 frames (which is a complex format). Maybe over some header_ops callback? - Alex -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello Alexander, On 07/02/2018 11:54 AM, Alexander Aring wrote: > Hi, > > On Tue, Jun 19, 2018 at 04:44:06PM -0700, Michael Scott wrote: >> After decompression of 6lowpan socket data, an IPv6 header is inserted >> before the existing socket payload. After this, we reset the >> network_header value of the skb to account for the difference in payload >> size from prior to decompression + the addition of the IPv6 header. >> >> However, we fail to reset the mac_header value. >> >> Leaving the mac_header value untouched here, can cause a calculation >> error in net/packet/af_packet.c packet_rcv() function when an >> AF_PACKET socket is opened in SOCK_RAW mode for use on a 6lowpan >> interface. >> >> On line 2088, the data pointer is moved backward by the value returned >> from skb_mac_header(). If skb->data is adjusted so that it is before >> the skb->head pointer (which can happen when an old value of mac_header >> is left in place) the kernel generates a panic in net/core/skbuff.c >> line 1717. >> >> This panic can be generated by BLE 6lowpan interfaces (such as bt0) and >> 802.15.4 interfaces (such as lowpan0) as they both use the same 6lowpan >> sources for compression and decompression. >> >> Signed-off-by: Michael Scott <michael@opensourcefoundries.com> >> --- >> net/6lowpan/iphc.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c >> index 6b1042e21656..52fad5dad9f7 100644 >> --- a/net/6lowpan/iphc.c >> +++ b/net/6lowpan/iphc.c >> @@ -770,6 +770,7 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev, >> hdr.hop_limit, &hdr.daddr); >> >> skb_push(skb, sizeof(hdr)); >> + skb_reset_mac_header(skb); >> skb_reset_network_header(skb); >> skb_copy_to_linear_data(skb, &hdr, sizeof(hdr)); >> > I think it's good to make that if the mac_header gets a dangled pointer. > But we don't have a mac header at this point anymore... > > There exists also some functionality that the MAC header is not set, I > suppose this can be usefuly for tun like interfaces e.g. RAW IP what we > have here. > > skb_mac_header_was_set > > which does: > > return skb->mac_header != (typeof(skb->mac_header))~0U; > > maybe we can set it as (typeof(skb->mac_header))~0U and then everything > will run as far the kernel will not crash anymore. > > Question is for me: which upper layer wants access MAC header here on > receive path? > It cannot parsed anyhow because so far I know no upper layer can parse > at the moment 802.15.4 frames (which is a complex format). Maybe over > some header_ops callback? I was testing a C program which performs NAT64 handling on packets destined to a certain IPv6 subnet (64:ff9b::). To do this, the application opens a RAW socket like this: sniff_sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); It then sets promiscuous mode and enters a looping call of: length = recv(sniff_sock, buffer, PACKET_BUFFER, MSG_TRUNC); My host PC kernel would then promptly crash on me. (I'm going to purposely avoid the obvious point of: this probably isn't the best way to parse packets for NAT64 translation as you will get every single packet incoming or outgoing on the host.) Turns out, testing the program on an 802.15.4 6lowpan interface exposed some of the issues which this mailing list (but not myself) is well aware of (no L2 data in the RAW packets) and also led me to debugging this patch to stop the kernel crash. TL;DR: To summarize, any PF_PACKET SOCK_RAW socket which recv()'s IPv6 data from a 6lowpan node will cause this kernel crash eventually (checked on kernel 4.15, 4.16, 4.17 and 4.18-rc1). - Mike > > - Alex -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Jun 19, 2018 at 04:44:06PM -0700, Michael Scott wrote: > After decompression of 6lowpan socket data, an IPv6 header is inserted > before the existing socket payload. After this, we reset the > network_header value of the skb to account for the difference in payload > size from prior to decompression + the addition of the IPv6 header. > > However, we fail to reset the mac_header value. > > Leaving the mac_header value untouched here, can cause a calculation > error in net/packet/af_packet.c packet_rcv() function when an > AF_PACKET socket is opened in SOCK_RAW mode for use on a 6lowpan > interface. > > On line 2088, the data pointer is moved backward by the value returned > from skb_mac_header(). If skb->data is adjusted so that it is before > the skb->head pointer (which can happen when an old value of mac_header > is left in place) the kernel generates a panic in net/core/skbuff.c > line 1717. > > This panic can be generated by BLE 6lowpan interfaces (such as bt0) and > 802.15.4 interfaces (such as lowpan0) as they both use the same 6lowpan > sources for compression and decompression. > > Signed-off-by: Michael Scott <michael@opensourcefoundries.com> Acked-by: Alexander Aring <aring@mojatatu.com> Thanks! - Alex -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello Jukka. On 20.06.2018 01:44, Michael Scott wrote: > After decompression of 6lowpan socket data, an IPv6 header is inserted > before the existing socket payload. After this, we reset the > network_header value of the skb to account for the difference in payload > size from prior to decompression + the addition of the IPv6 header. > > However, we fail to reset the mac_header value. > > Leaving the mac_header value untouched here, can cause a calculation > error in net/packet/af_packet.c packet_rcv() function when an > AF_PACKET socket is opened in SOCK_RAW mode for use on a 6lowpan > interface. > > On line 2088, the data pointer is moved backward by the value returned > from skb_mac_header(). If skb->data is adjusted so that it is before > the skb->head pointer (which can happen when an old value of mac_header > is left in place) the kernel generates a panic in net/core/skbuff.c > line 1717. > > This panic can be generated by BLE 6lowpan interfaces (such as bt0) and > 802.15.4 interfaces (such as lowpan0) as they both use the same 6lowpan > sources for compression and decompression. > > Signed-off-by: Michael Scott <michael@opensourcefoundries.com> > --- > net/6lowpan/iphc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c > index 6b1042e21656..52fad5dad9f7 100644 > --- a/net/6lowpan/iphc.c > +++ b/net/6lowpan/iphc.c > @@ -770,6 +770,7 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev, > hdr.hop_limit, &hdr.daddr); > > skb_push(skb, sizeof(hdr)); > + skb_reset_mac_header(skb); > skb_reset_network_header(skb); > skb_copy_to_linear_data(skb, &hdr, sizeof(hdr)); > > Alex acked this patch for the ieee802154 side. Could you test it for the bluetooth 6lowpan side and ack or nack as well? So far plain 6lowpan subsystem patches would still go through the bluetooth tree after Alex and you acked them. I guess Marcel or Johan just waiting for your review. regards Stefan Schmidt -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 2018-06-19 at 16:44 -0700, Michael Scott wrote: > After decompression of 6lowpan socket data, an IPv6 header is > inserted > before the existing socket payload. After this, we reset the > network_header value of the skb to account for the difference in > payload > size from prior to decompression + the addition of the IPv6 header. > > > Signed-off-by: Michael Scott <michael@opensourcefoundries.com> > --- > net/6lowpan/iphc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c > index 6b1042e21656..52fad5dad9f7 100644 > --- a/net/6lowpan/iphc.c > +++ b/net/6lowpan/iphc.c > @@ -770,6 +770,7 @@ int lowpan_header_decompress(struct sk_buff *skb, > const struct net_device *dev, > hdr.hop_limit, &hdr.daddr); > > skb_push(skb, sizeof(hdr)); > + skb_reset_mac_header(skb); > skb_reset_network_header(skb); > skb_copy_to_linear_data(skb, &hdr, sizeof(hdr)); > Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com> Cheers, Jukka -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello. On 20.06.2018 01:44, Michael Scott wrote: > After decompression of 6lowpan socket data, an IPv6 header is inserted > before the existing socket payload. After this, we reset the > network_header value of the skb to account for the difference in payload > size from prior to decompression + the addition of the IPv6 header. > > However, we fail to reset the mac_header value. > > Leaving the mac_header value untouched here, can cause a calculation > error in net/packet/af_packet.c packet_rcv() function when an > AF_PACKET socket is opened in SOCK_RAW mode for use on a 6lowpan > interface. > > On line 2088, the data pointer is moved backward by the value returned > from skb_mac_header(). If skb->data is adjusted so that it is before > the skb->head pointer (which can happen when an old value of mac_header > is left in place) the kernel generates a panic in net/core/skbuff.c > line 1717. > > This panic can be generated by BLE 6lowpan interfaces (such as bt0) and > 802.15.4 interfaces (such as lowpan0) as they both use the same 6lowpan > sources for compression and decompression. > > Signed-off-by: Michael Scott <michael@opensourcefoundries.com> > --- > net/6lowpan/iphc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c > index 6b1042e21656..52fad5dad9f7 100644 > --- a/net/6lowpan/iphc.c > +++ b/net/6lowpan/iphc.c > @@ -770,6 +770,7 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev, > hdr.hop_limit, &hdr.daddr); > > skb_push(skb, sizeof(hdr)); > + skb_reset_mac_header(skb); > skb_reset_network_header(skb); > skb_copy_to_linear_data(skb, &hdr, sizeof(hdr)); This showed no problems in my ieee802154 + 6lowpan tests. Acked-by: Stefan Schmidt <stefan@datenfreihafen.org> regards Stefan Schmidt -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Michael, > After decompression of 6lowpan socket data, an IPv6 header is inserted > before the existing socket payload. After this, we reset the > network_header value of the skb to account for the difference in payload > size from prior to decompression + the addition of the IPv6 header. > > However, we fail to reset the mac_header value. > > Leaving the mac_header value untouched here, can cause a calculation > error in net/packet/af_packet.c packet_rcv() function when an > AF_PACKET socket is opened in SOCK_RAW mode for use on a 6lowpan > interface. > > On line 2088, the data pointer is moved backward by the value returned > from skb_mac_header(). If skb->data is adjusted so that it is before > the skb->head pointer (which can happen when an old value of mac_header > is left in place) the kernel generates a panic in net/core/skbuff.c > line 1717. > > This panic can be generated by BLE 6lowpan interfaces (such as bt0) and > 802.15.4 interfaces (such as lowpan0) as they both use the same 6lowpan > sources for compression and decompression. > > Signed-off-by: Michael Scott <michael@opensourcefoundries.com> > --- > net/6lowpan/iphc.c | 1 + > 1 file changed, 1 insertion(+) patch has been applied to bluetooth-next tree. Regards Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-wpan" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c index 6b1042e21656..52fad5dad9f7 100644 --- a/net/6lowpan/iphc.c +++ b/net/6lowpan/iphc.c @@ -770,6 +770,7 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev, hdr.hop_limit, &hdr.daddr); skb_push(skb, sizeof(hdr)); + skb_reset_mac_header(skb); skb_reset_network_header(skb); skb_copy_to_linear_data(skb, &hdr, sizeof(hdr));
After decompression of 6lowpan socket data, an IPv6 header is inserted before the existing socket payload. After this, we reset the network_header value of the skb to account for the difference in payload size from prior to decompression + the addition of the IPv6 header. However, we fail to reset the mac_header value. Leaving the mac_header value untouched here, can cause a calculation error in net/packet/af_packet.c packet_rcv() function when an AF_PACKET socket is opened in SOCK_RAW mode for use on a 6lowpan interface. On line 2088, the data pointer is moved backward by the value returned from skb_mac_header(). If skb->data is adjusted so that it is before the skb->head pointer (which can happen when an old value of mac_header is left in place) the kernel generates a panic in net/core/skbuff.c line 1717. This panic can be generated by BLE 6lowpan interfaces (such as bt0) and 802.15.4 interfaces (such as lowpan0) as they both use the same 6lowpan sources for compression and decompression. Signed-off-by: Michael Scott <michael@opensourcefoundries.com> --- net/6lowpan/iphc.c | 1 + 1 file changed, 1 insertion(+)