bpf, sockmap: Check for any of tcp_bpf_prots when cloning a listener

Overview

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

bpf, sockmap: Check for any of tcp_bpf_prots when cloning a listener

A listening socket linked to a sockmap has its sk_prot overridden. It points to one of the struct proto variants in tcp_bpf_prots. The variant depends on the socket's family and which sockmap programs are attached.

A child socket cloned from a TCP listener initially inherits their sk_prot. But before cloning is finished, we restore the child's proto to the listener's original non-tcp_bpf_prots one. This happens in tcp_create_openreq_child -> tcp_bpf_clone.

Today, in tcp_bpf_clone we detect if the child's proto should be restored by checking only for the TCP_BPF_BASE proto variant. This is not correct. The sk_prot of listening socket linked to a sockmap can point to to any variant in tcp_bpf_prots.

If the listeners sk_prot happens to be not the TCP_BPF_BASE variant, then the child socket unintentionally is left if the inherited sk_prot by tcp_bpf_clone.

This leads to issues like infinite recursion on close 1, because the child state is otherwise not set up for use with tcp_bpf_prot operations.

Adjust the check in tcp_bpf_clone to detect all of tcp_bpf_prots variants.

Note that it wouldn't be sufficient to check the socket state when overriding the sk_prot in tcp_bpf_update_proto in order to always use the TCP_BPF_BASE variant for listening sockets. Since commit b8b8315e39ff ("bpf, sockmap: Remove unhash handler for BPF sockmap usage") it is possible for a socket to transition to TCP_LISTEN state while already linked to a sockmap, e.g. connect() -> insert into map -> connect(AF_UNSPEC) -> listen().

Affected

• Linux >= e80251555f0befd1271e74b080bccf0ff0348bfc < 9bd6074e1872d22190a8da30e796cbf937d334f0
• Linux >= e80251555f0befd1271e74b080bccf0ff0348bfc < c681d7a4ed3d360de0574f4d6b7305a8de8dc54f
• Linux >= e80251555f0befd1271e74b080bccf0ff0348bfc < 12b0ec7c6953e1602957926439e5297095d7d065
• Linux >= e80251555f0befd1271e74b080bccf0ff0348bfc < ddce1e091757d0259107c6c0c7262df201de2b66
• Linux 5.7

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.