KMSAN: uninit-value in do_msgrcv

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    8fc8ecd1c58a kmsan: unpoison regs in arch_uprobe_exception..
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=1481799f800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9fa436d3ae606638
dashboard link: https://syzkaller.appspot.com/bug?extid=2827ef6b3385deb07eaf
compiler:       clang version 7.0.0 (trunk 332596)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1265edb7800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16eeee9f800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2827ef6b3385deb07eaf@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KMSAN: uninit-value in do_msgrcv+0x509/0x1e30 ipc/msg.c:1048
CPU: 0 PID: 4528 Comm: syz-executor852 Not tainted 4.17.0-rc5+ #103
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+0x185/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x149/0x260 mm/kmsan/kmsan.c:1084
 __msan_warning_32+0x6e/0xc0 mm/kmsan/kmsan_instr.c:686
 do_msgrcv+0x509/0x1e30 ipc/msg.c:1048
 ksys_msgrcv ipc/msg.c:1184 [inline]
 __do_sys_msgrcv ipc/msg.c:1190 [inline]
 __se_sys_msgrcv ipc/msg.c:1187 [inline]
 __x64_sys_msgrcv+0x160/0x1b0 ipc/msg.c:1187
 do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4459b9
RSP: 002b:00007f0d57662db8 EFLAGS: 00000297 ORIG_RAX: 0000000000000046
RAX: ffffffffffffffda RBX: 00000000006dac54 RCX: 00000000004459b9
RDX: 00000000000000d0 RSI: 0000000020000000 RDI: 0000000000260007
RBP: 00000000006dac50 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000000
R13: 00007ffd5ab7e25f R14: 00007f0d576639c0 R15: 0000000000000006

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:189
 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:315
 __kmalloc_node+0xe25/0x11f0 mm/slub.c:3865
 kmalloc_node include/linux/slab.h:554 [inline]
 kvmalloc_node+0x197/0x2f0 mm/util.c:421
 kvmalloc include/linux/mm.h:550 [inline]
 newque+0xb4/0x7d0 ipc/msg.c:139
 ipcget_new ipc/util.c:315 [inline]
 ipcget+0x27b/0xd90 ipc/util.c:653
 ksys_msgget ipc/msg.c:289 [inline]
 __do_sys_msgget ipc/msg.c:294 [inline]
 __se_sys_msgget ipc/msg.c:292 [inline]
 __x64_sys_msgget+0x14c/0x1d0 ipc/msg.c:292
 do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
==================================================================


---
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