linux-kernel - Re: [syzbot] [kernel?] KMSAN: kernel-infoleak in vmci_host_unlocked

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Message-ID: <68591e22.a00a0220.34b642.0006.GAE@google.com>
Date: Mon, 23 Jun 2025 02:28:02 -0700
From: syzbot <syzbot+9b9124ae9b12d5af5d95@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, lizhi.xu@...driver.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [kernel?] KMSAN: kernel-infoleak in vmci_host_unlocked_ioctl
 (3)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: kernel-infoleak in vmci_host_unlocked_ioctl

=====================================================
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:442 [inline]
 vmci_host_unlocked_ioctl+0x1d6f/0x52d0 drivers/misc/vmw_vmci/vmci_host.c:942
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0x239/0x400 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 filename created at:
 ima_file_mprotect+0x78/0x800 security/integrity/ima/ima_main.c:500
 security_file_mprotect+0x141/0x590 security/security.c:3012

Bytes 28-31 of 40 are uninitialized
Memory access of size 40 starts at ffff888021ad2880
Data copied to user address 000000000000a4bf

CPU: 1 UID: 0 PID: 6749 Comm: syz.0.16 Not tainted 6.16.0-rc3-syzkaller-g86731a2a651e-dirty #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
=====================================================


Tested on:

commit:         86731a2a Linux 6.16-rc3
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=112fdb0c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=595d344ff0b23ac5
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16bff370580000