CVE-2023-53517

In the Linux kernel, the following vulnerability has been resolved:

tipc: do not update mtu if msg_max is too small in mtu negotiation

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.