On Mon, May 1, 2023 at 1:22 AM Tung Quang Nguyen < tung.q.ngu...@dektech.com.au> wrote:
> > > >-----Original Message----- > >From: Xin Long <lucien....@gmail.com> > >Sent: Sunday, April 30, 2023 5:41 AM > >To: network dev <net...@vger.kernel.org>; > tipc-discussion@lists.sourceforge.net > >Cc: da...@davemloft.net; k...@kernel.org; Eric Dumazet < > eduma...@google.com>; Paolo Abeni <pab...@redhat.com>; Jon Maloy > ><jma...@redhat.com> > >Subject: [PATCH net 2/2] tipc: do not update mtu if msg_max is too small > > > >When doing link mtu negotiation, a malicious peer may send Activate msg > >with a very small mtu, e.g. 4 in Shuang's testing, without checking for > >the minimum mtu, l->mtu will be set to 4 in tipc_link_proto_rcv(), then > >n->links[bearer_id].mtu is set to 4294967228, which is a overflow of > >'4 - INT_H_SIZE - EMSG_OVERHEAD' in tipc_link_mss(). > > > >With tipc_link.mtu = 4, tipc_link_xmit() kept printing the warning: > > > > tipc: Too large msg, purging xmit list 1 5 0 40 4! > > tipc: Too large msg, purging xmit list 1 15 0 60 4! > > > >And with tipc_link_entry.mtu 4294967228, a huge skb was allocated in > >named_distribute(), and when purging it in tipc_link_xmit(), a crash > >was even caused: > > > > general protection fault, probably for non-canonical address > 0x2100001011000dd: 0000 [#1] PREEMPT SMP PTI > > CPU: 0 PID: 0 Comm: swapper/0 Kdump: loaded Not tainted 6.3.0.neta #19 > > RIP: 0010:kfree_skb_list_reason+0x7e/0x1f0 > > Call Trace: > > <IRQ> > > skb_release_data+0xf9/0x1d0 > > kfree_skb_reason+0x40/0x100 > > tipc_link_xmit+0x57a/0x740 [tipc] > > tipc_node_xmit+0x16c/0x5c0 [tipc] > > tipc_named_node_up+0x27f/0x2c0 [tipc] > > tipc_node_write_unlock+0x149/0x170 [tipc] > > tipc_rcv+0x608/0x740 [tipc] > > tipc_udp_recv+0xdc/0x1f0 [tipc] > > udp_queue_rcv_one_skb+0x33e/0x620 > > udp_unicast_rcv_skb.isra.72+0x75/0x90 > > __udp4_lib_rcv+0x56d/0xc20 > > ip_protocol_deliver_rcu+0x100/0x2d0 > > > >This patch fixes it by checking the new mtu against tipc_bearer_min_mtu(), > >and not updating mtu if it is too small. > > > >Fixes: ed193ece2649 ("tipc: simplify link mtu negotiation") > >Reported-by: Shuang Li <shu...@redhat.com> > >Signed-off-by: Xin Long <lucien....@gmail.com> > >--- > > net/tipc/link.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > >diff --git a/net/tipc/link.c b/net/tipc/link.c > >index b3ce24823f50..a9e46c58b28a 100644 > >--- a/net/tipc/link.c > >+++ b/net/tipc/link.c > >@@ -2200,7 +2200,7 @@ static int tipc_link_proto_rcv(struct tipc_link *l, > struct sk_buff *skb, > > struct tipc_msg *hdr = buf_msg(skb); > > struct tipc_gap_ack_blks *ga = NULL; > > bool reply = msg_probe(hdr), retransmitted = false; > >- u32 dlen = msg_data_sz(hdr), glen = 0; > >+ u32 dlen = msg_data_sz(hdr), glen = 0, msg_max; > > u16 peers_snd_nxt = msg_next_sent(hdr); > > u16 peers_tol = msg_link_tolerance(hdr); > > u16 peers_prio = msg_linkprio(hdr); > >@@ -2283,8 +2283,9 @@ static int tipc_link_proto_rcv(struct tipc_link *l, > struct sk_buff *skb, > > l->peer_session = msg_session(hdr); > > l->in_session = true; > > l->peer_bearer_id = msg_bearer_id(hdr); > >- if (l->mtu > msg_max_pkt(hdr)) > >- l->mtu = msg_max_pkt(hdr); > >+ msg_max = msg_max_pkt(hdr); > >+ if (msg_max >= tipc_bearer_min_mtu(l->net, l->bearer_id) > && l->mtu > msg_max) > >+ l->mtu = msg_max; > If this link receives a malicious ACTIVATE_MSG from a peer, this message > should be dropped. It is better if the check " msg_max < > tipc_bearer_min_mtu()" is put at the beginning of this ACTIVATE_MSG > handling and we break immediately. > > Sounds good, will move 'msg_max < tipc_bearer_min_mtu()' up. Thanks for reviewing. _______________________________________________ tipc-discussion mailing list tipc-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tipc-discussion