CVE-2021-47591

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> mptcp: remove tcp ulp setsockopt support<br /> <br /> TCP_ULP setsockopt cannot be used for mptcp because its already<br /> used internally to plumb subflow (tcp) sockets to the mptcp layer.<br /> <br /> syzbot managed to trigger a crash for mptcp connections that are<br /> in fallback mode:<br /> <br /> KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]<br /> CPU: 1 PID: 1083 Comm: syz-executor.3 Not tainted 5.16.0-rc2-syzkaller #0<br /> RIP: 0010:tls_build_proto net/tls/tls_main.c:776 [inline]<br /> [..]<br /> __tcp_set_ulp net/ipv4/tcp_ulp.c:139 [inline]<br /> tcp_set_ulp+0x428/0x4c0 net/ipv4/tcp_ulp.c:160<br /> do_tcp_setsockopt+0x455/0x37c0 net/ipv4/tcp.c:3391<br /> mptcp_setsockopt+0x1b47/0x2400 net/mptcp/sockopt.c:638<br /> <br /> Remove support for TCP_ULP setsockopt.