[syzbot] [kernel?] KMSAN: kernel-infoleak in vmci_host_unlocked_ioctl (3)

[syzbot <syzbot+9b9124ae9b12d5af5d95@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    08215f5486ec Merge tag 'kbuild-fixes-v6.16' of git://git.k..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13f7fd70580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=61539536677af51c
dashboard link: https://syzkaller.appspot.com/bug?extid=9b9124ae9b12d5af5d95
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f7fd70580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1485690c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/01c395d764eb/disk-08215f54.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/15fc58e6441d/vmlinux-08215f54.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dbd5ac78ef83/bzImage-08215f54.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9b9124ae9b12d5af5d95@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in _inline_copy_to_user include/linux/uaccess.h:196 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_user+0xcc/0x120 lib/usercopy.c:26
 instrument_copy_to_user include/linux/instrumented.h:114 [inline]
 _inline_copy_to_user include/linux/uaccess.h:196 [inline]
 _copy_to_user+0xcc/0x120 lib/usercopy.c:26
 copy_to_user include/linux/uaccess.h:225 [inline]
 vmci_host_do_receive_datagram drivers/misc/vmw_vmci/vmci_host.c:438 [inline]
 vmci_host_unlocked_ioctl+0x1e7e/0x5200 drivers/misc/vmw_vmci/vmci_host.c:932
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0x23c/0x400 fs/ioctl.c:893
 __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:893
 x64_sys_call+0x1ebe/0x3db0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable __x.i.i created at:
 set_xfeature_in_sigframe arch/x86/kernel/fpu/xstate.h:81 [inline]
 save_xstate_epilog arch/x86/kernel/fpu/signal.c:140 [inline]
 copy_fpstate_to_sigframe+0x11f2/0x13d0 arch/x86/kernel/fpu/signal.c:232
 get_sigframe+0xc6a/0x1020 arch/x86/kernel/signal.c:163

Bytes 28-31 of 40 are uninitialized
Memory access of size 40 starts at ffff888131f74080
Data copied to user address 000000000000a4bf

CPU: 1 UID: 0 PID: 5798 Comm: syz-executor419 Not tainted 6.16.0-rc1-syzkaller-00239-g08215f5486ec #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
=====================================================


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