CVE-2025-23145

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

mptcp: fix NULL pointer in can_accept_new_subflow

When testing valkey benchmark tool with MPTCP, the kernel panics in mptcp_can_accept_new_subflow because subflow_req->msk is NULL.

Call trace:

mptcp_can_accept_new_subflow (./net/mptcp/subflow.c:63 (discriminator 4)) (P) subflow_syn_recv_sock (./net/mptcp/subflow.c:854) tcp_check_req (./net/ipv4/tcp_minisocks.c:863) tcp_v4_rcv (./net/ipv4/tcp_ipv4.c:2268) ip_protocol_deliver_rcu (./net/ipv4/ip_input.c:207) ip_local_deliver_finish (./net/ipv4/ip_input.c:234) ip_local_deliver (./net/ipv4/ip_input.c:254) ip_rcv_finish (./net/ipv4/ip_input.c:449) …

According to the debug log, the same req received two SYN-ACK in a very short time, very likely because the client retransmits the syn ack due to multiple reasons.

Even if the packets are transmitted with a relevant time interval, they can be processed by the server on different CPUs concurrently). The subflow_req->msk ownership is transferred to the subflow the first, and there will be a risk of a null pointer dereference here.

This patch fixes this issue by moving the subflow_req->msk under the own_req == true conditional.

Note that the !msk check in subflow_hmac_valid() can be dropped, because the same check already exists under the own_req mpj branch where the code has been moved to.

Affected Software

References

• https://git.kernel.org/stable/c/443041deb5ef6a1289a99ed95015ec7442f141dc
• https://git.kernel.org/stable/c/4b2649b9717678aeb097893cc49f59311a1ecab0
• https://git.kernel.org/stable/c/7f9ae060ed64aef8f174c5f1ea513825b1be9af1
• https://git.kernel.org/stable/c/855bf0aacd51fced11ea9aa0d5101ee0febaeadb
• https://git.kernel.org/stable/c/8cf7fef1bb2ffea7792bcbf71ca00216cecc725d
• https://git.kernel.org/stable/c/b3088bd2a6790c8efff139d86d7a9d0b1305977b
• https://git.kernel.org/stable/c/dc81e41a307df523072186b241fa8244fecd7803
• https://git.kernel.org/stable/c/efd58a8dd9e7a709a90ee486a4247c923d27296f