CVE-2025-21854 Information

Description

In the Linux kernel the following vulnerability has been resolved:

sockmap vsock: For connectible sockets allow only connected

sockmap expects all vsocks to have a transport assigned which is expressed in vsock_proto::psock_update_sk_prot(). However there is an edge case where an unconnected (connectible) socket may lose its previously assigned transport. This is handled with a NULL check in the vsock/BPF recv path.

Another design detail is that listening vsocks are not supposed to have any transport assigned at all. Which implies they are not supported by the sockmap. But this is complicated by the fact that a socket before switching to TCP_LISTEN may have had some transport assigned during a failed connect() attempt. Hence we may end up with a listening vsock in a sockmap which blows up quickly:

KASAN: null-ptr-deref in range [0x0000000000000120-0x0000000000000127] CPU: 7 UID: 0 PID: 56 Comm: kworker/7:0 Not tainted 6.14.0-rc1+ Workqueue: vsock-loopback vsock_loopback_work RIP: 0010:vsock_read_skb+0x4b/0x90 Call Trace: sk_psock_verdict_data_ready+0xa4/0x2e0 virtio_transport_recv_pkt+0x1ca8/0x2acc vsock_loopback_work+0x27d/0x3f0 process_one_work+0x846/0x1420 worker_thread+0x5b3/0xf80 kthread+0x35a/0x700 ret_from_fork+0x2d/0x70 ret_from_fork_asm+0x1a/0x30

For connectible sockets instead of relying solely on the state of vsk->transport tell sockmap to only allow those representing established connections. This aligns with the behaviour for AF_INET and AF_UNIX.

Reference

https://git.kernel.org/stable/c/22b683217ad2112791a708693cb236507abd637a https://git.kernel.org/stable/c/8fb5bb169d17cdd12c2dcc2e96830ed487d77a0f https://git.kernel.org/stable/c/cc9a7832ede53ade1ba9991f0e27314caa4029d8 https://git.kernel.org/stable/c/f7b473e35986835cc2813fef7b9d40336a09247e