KMSAN: kernel-infoleak in _copy_to_iter (3)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    22ec98c3e38f kmsan: unpoison pt_regs in do_nmi()
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=16eeedd6400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4f3dcd8312e87223
dashboard link: https://syzkaller.appspot.com/bug?extid=057458894bc8cada4dee
compiler:       clang version 8.0.0 (trunk 339414)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11daa385400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=102890f6400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+057458894bc8cada4dee@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KMSAN: kernel-infoleak in copyout lib/iov_iter.c:140 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x471/0x2640 lib/iov_iter.c:571
CPU: 0 PID: 6126 Comm: syz-executor340 Not tainted 4.19.0-rc7+ #69
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+0x306/0x460 lib/dump_stack.c:113
 kmsan_report+0x1a2/0x2e0 mm/kmsan/kmsan.c:917
 kmsan_internal_check_memory+0x374/0x460 mm/kmsan/kmsan.c:997
 kmsan_copy_to_user+0x89/0xe0 mm/kmsan/kmsan_hooks.c:552
 copyout lib/iov_iter.c:140 [inline]
 _copy_to_iter+0x471/0x2640 lib/iov_iter.c:571
 copy_to_iter include/linux/uio.h:106 [inline]
 skb_copy_datagram_iter+0x4c3/0x1040 net/core/datagram.c:431
 skb_copy_datagram_msg include/linux/skbuff.h:3279 [inline]
 tipc_recvmsg+0xd12/0x1c20 net/tipc/socket.c:1739
 sock_recvmsg_nosec net/socket.c:794 [inline]
 sock_recvmsg net/socket.c:801 [inline]
 sock_read_iter+0x45a/0x4e0 net/socket.c:878
 call_read_iter include/linux/fs.h:1802 [inline]
 new_sync_read fs/read_write.c:406 [inline]
 __vfs_read+0x874/0xb00 fs/read_write.c:418
 vfs_read+0x36f/0x6a0 fs/read_write.c:452
 ksys_read fs/read_write.c:578 [inline]
 __do_sys_read fs/read_write.c:588 [inline]
 __se_sys_read+0x183/0x370 fs/read_write.c:586
 __x64_sys_read+0x4a/0x70 fs/read_write.c:586
 do_syscall_64+0xbe/0x100 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x445629
Code: e8 6c b6 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 2b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb1d321cdb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00000000006dac28 RCX: 0000000000445629
RDX: 00000000000000f7 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000006dac20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac2c
R13: 00007fff668b970f R14: 00007fb1d321d9c0 R15: 00000000006dad2c

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:255 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:270 [inline]
 kmsan_internal_chain_origin+0x136/0x240 mm/kmsan/kmsan.c:572
 kmsan_memcpy_origins+0x13d/0x1b0 mm/kmsan/kmsan.c:396
 __msan_memcpy+0xcf/0x150 mm/kmsan/kmsan_instr.c:286
 tipc_group_create_event+0x672/0xb90 net/tipc/group.c:689
 tipc_group_proto_rcv+0x26a5/0x38f0 net/tipc/group.c:769
 tipc_sk_proto_rcv net/tipc/socket.c:1947 [inline]
 tipc_sk_filter_rcv+0x2948/0x3a40 net/tipc/socket.c:2113
 tipc_sk_enqueue net/tipc/socket.c:2194 [inline]
 tipc_sk_rcv+0xcbe/0x2b10 net/tipc/socket.c:2238
 tipc_node_xmit+0x2f1/0xa00 net/tipc/node.c:1361
 tipc_node_xmit_skb net/tipc/node.c:1410 [inline]
 tipc_node_distr_xmit+0x40d/0x680 net/tipc/node.c:1425
 tipc_sk_rcv+0x1e52/0x2b10 net/tipc/socket.c:2242
 tipc_topsrv_kern_evt net/tipc/topsrv.c:618 [inline]
 tipc_conn_send_to_sock net/tipc/topsrv.c:291 [inline]
 tipc_conn_send_work+0x82e/0xe20 net/tipc/topsrv.c:311
 process_one_work+0x19c4/0x24f0 kernel/workqueue.c:2153
 worker_thread+0x206d/0x2b30 kernel/workqueue.c:2296
 kthread+0x59c/0x5d0 kernel/kthread.c:247
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:416

Local variable description: ----evt.sroa.11@tipc_group_create_event
Variable was created at:
 tipc_group_create_event+0xbf/0xb90 net/tipc/group.c:664
 tipc_group_proto_rcv+0x26a5/0x38f0 net/tipc/group.c:769

Bytes 32-47 of 48 are uninitialized
Memory access of size 48 starts at ffff8801beafd0bc
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches