rds: Fix inet6_addr_lst NULL dereference when IPv6 is disabled

Summary

In the Linux kernel, the following vulnerability has been resolved: rds: Fix inet6_addr_lst NULL dereference when IPv6 is disabled When booting with the 'ipv6.disable=1' parameter, inet6_addr_lst is never initialized because inet6_init() exits before addrconf_init() is called to initialize it. An attempt to bind an RDS socket to an ipv6 address results in a crash in __ipv6_chk_addr_and_flags() KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] RIP: 0010:__ipv6_chk_addr_and_flags+0x1df/0x7e0 Call Trace: <TASK> ipv6_chk_addr+0x3b/0x50 rds_tcp_laddr_check+0x155/0x3b0 [rds_tcp] rds_trans_get_preferred+0x15d/0x2d0 [rds] ? trace_hardirqs_on+0x2d/0x110 rds_bind+0x1433/0x1d60 [rds] ? rds_remove_bound+0xd50/0xd50 [rds] ? aa_af_perm+0x250/0x250 ? __might_fault+0xde/0x190 ? __sys_bind+0x1dc/0x210 __sys_bind+0x1dc/0x210 ? __ia32_sys_socketpair+0x100/0x100 ? restore_fpregs_from_fpstate+0x53/0x100 __x64_sys_bind+0x73/0xb0 ? syscall_enter_from_user_mode+0x1c/0x50 do_syscall_64+0x34/0x80 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 RIP: 0033:0x7f47f8269ea9 </TASK> The following code reproduces the issue: struct sockaddr_in6 addr; s = socket(PF_RDS, SOCK_SEQPACKET, 0); memset(&addr, 0, sizeof(addr)); inet_pton(AF_INET6, ADDRESS, &addr.sin6_addr); addr.sin6_family = AF_INET6; addr.sin6_port = htons(PORT); bind(s, &addr, sizeof(addr)); Found by InfoTeCS on behalf of Linux Verification Center (linuxtesting.org) with Syzkaller.