mptcp: fix NULL pointer in can_accept_new_subflow
commit 443041de upstream. 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. Fixes: 9466a1cc ("mptcp: enable JOIN requests even if cookies are in use") Cc: stable@vger.kernel.org Suggested-by:Paolo Abeni <pabeni@redhat.com> Signed-off-by:
Gang Yan <yangang@kylinos.cn> Reviewed-by:
Matthieu Baerts (NGI0) <matttbe@kernel.org> Signed-off-by:
Jakub Kicinski <kuba@kernel.org> [ Conflict in subflow.c because commit 74c7dfbe ("mptcp: consolidate in_opt sub-options fields in a bitmask") is not in this version. The conflict is in the context, and the modification can still be applied. Note that subflow_add_reset_reason() is not needed here, because the related feature is not supported in this version. ] Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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