KMSAN: uninit-value in do_dccp_getsockopt

Hello,

syzbot found the following crash on:

HEAD commit:    c95d0c95 kmsan: block: skip bio block merging logic for KM..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x3677bbe00000
kernel config:  https://syzkaller.appspot.com/x/.config?xx11db4cc444a7f6
dashboard link: https://syzkaller.appspot.com/bug?extidÞ5579bd3a5d86b1e863
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email protected]

==========================BUG: KMSAN: uninit-value in ccid_hc_rx_getsockopt net/dccp/ccids/../ccid.h:246 [inline]
BUG: KMSAN: uninit-value in do_dccp_getsockopt+0x1851/0x1e10 net/dccp/proto.c:671
CPU: 1 PID: 28577 Comm: syz-executor.1 Not tainted 5.6.0-rc7-syzkaller #0
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+0x1c9/0x220 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
 ccid_hc_rx_getsockopt net/dccp/ccids/../ccid.h:246 [inline]
 do_dccp_getsockopt+0x1851/0x1e10 net/dccp/proto.c:671
 dccp_getsockopt+0xfd/0x200 net/dccp/proto.c:694
 sock_common_getsockopt+0x13f/0x180 net/core/sock.c:3111
 __sys_getsockopt+0x533/0x7b0 net/socket.c:2177
 __do_sys_getsockopt net/socket.c:2192 [inline]
 __se_sys_getsockopt+0xe1/0x100 net/socket.c:2189
 __x64_sys_getsockopt+0x62/0x80 net/socket.c:2189
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45c849
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f60866cdc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007f60866ce6d4 RCX: 000000000045c849
RDX: 00000000000000a9 RSI: 000000000000010d RDI: 0000000000000004
RBP: 000000000076bf00 R08: 00000000200000c0 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000174 R14: 00000000004c3f3e R15: 000000000076bf0c

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127
 kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:82
 slab_alloc_node mm/slub.c:2801 [inline]
 slab_alloc mm/slub.c:2810 [inline]
 kmem_cache_alloc+0x711/0xd70 mm/slub.c:2815
 ccid_new+0x1da/0x680 net/dccp/ccid.c:148
 dccp_hdlr_ccid+0x9f/0x260 net/dccp/feat.c:39
 __dccp_feat_activate net/dccp/feat.c:339 [inline]
 dccp_feat_activate_values+0x5e9/0x1660 net/dccp/feat.c:1537
 dccp_rcv_request_sent_state_process net/dccp/input.c:468 [inline]
 dccp_rcv_state_process+0x1a6d/0x2320 net/dccp/input.c:676
 dccp_v4_do_rcv+0x221/0x330 net/dccp/ipv4.c:684
 sk_backlog_rcv include/net/sock.h:963 [inline]
 __release_sock+0x2a3/0x5c0 net/core/sock.c:2440
 release_sock+0x99/0x2a0 net/core/sock.c:2956
 inet_wait_for_connect net/ipv4/af_inet.c:588 [inline]
 __inet_stream_connect+0xb05/0x1340 net/ipv4/af_inet.c:680
 inet_stream_connect+0x101/0x180 net/ipv4/af_inet.c:719
 __sys_connect_file net/socket.c:1859 [inline]
 __sys_connect+0x6f7/0x770 net/socket.c:1876
 __do_sys_connect net/socket.c:1887 [inline]
 __se_sys_connect+0x8d/0xb0 net/socket.c:1884
 __x64_sys_connect+0x4a/0x70 net/socket.c:1884
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
==========================

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