KMSAN: uninit-value in rds_bind

[syzbot <syzbot+915c9f99f3dbc4bd6cd1@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    2dca2cbde67a kmsan: fix build warnings with CONFIG_KMSAN=n
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=16db895a400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=820d6393634b55e3
dashboard link: https://syzkaller.appspot.com/bug?extid=915c9f99f3dbc4bd6cd1
compiler:       clang version 8.0.0 (trunk 339414)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1137bffe400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1521a7fe400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+915c9f99f3dbc4bd6cd1@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KMSAN: uninit-value in rds_bind+0x1f1/0x2360 net/rds/bind.c:174
CPU: 1 PID: 4497 Comm: syz-executor098 Not tainted 4.19.0-rc1+ #36
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x14b/0x190 lib/dump_stack.c:113
  kmsan_report+0x183/0x2b0 mm/kmsan/kmsan.c:956
  __msan_warning+0x70/0xc0 mm/kmsan/kmsan_instr.c:645
  rds_bind+0x1f1/0x2360 net/rds/bind.c:174
  __sys_bind+0x594/0x6f0 net/socket.c:1481
  __do_sys_bind net/socket.c:1492 [inline]
  __se_sys_bind net/socket.c:1490 [inline]
  __x64_sys_bind+0xd8/0x120 net/socket.c:1490
  do_syscall_64+0x15b/0x220 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x440099
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffb43cf578 EFLAGS: 00000213 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440099
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000213 R12: 0000000000401920
R13: 00000000004019b0 R14: 0000000000000000 R15: 0000000000000000

Local variable description: ----address@__sys_bind
Variable was created at:
  __sys_bind+0x6a/0x6f0 net/socket.c:1468
  __do_sys_bind net/socket.c:1492 [inline]
  __se_sys_bind net/socket.c:1490 [inline]
  __x64_sys_bind+0xd8/0x120 net/socket.c:1490
==================================================================


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