linux-kernel - Re: [syzbot] [kvm?] KMSAN: uninit-value in em_ret

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Message-ID: <000000000000671a09060f84808b@google.com>
Date: Mon, 22 Jan 2024 00:20:24 -0800
From: syzbot <syzbot+579eb95e588b48b4499c@...kaller.appspotmail.com>
To: bp@...en8.de, dave.hansen@...ux.intel.com, glider@...gle.com, 
	hpa@...or.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	mingo@...hat.com, n.zhandarovich@...tech.ru, nogikh@...gle.com, 
	pbonzini@...hat.com, seanjc@...gle.com, syzkaller-bugs@...glegroups.com, 
	tglx@...utronix.de, x86@...nel.org
Subject: Re: [syzbot] [kvm?] KMSAN: uninit-value in em_ret_far

syzbot has found a reproducer for the following issue on:

HEAD commit:    9f8413c4a66f Merge tag 'cgroup-for-6.8' of git://git.kerne..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=174e24d7e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=656820e61b758b15
dashboard link: https://syzkaller.appspot.com/bug?extid=579eb95e588b48b4499c
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13ffebbde80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=143dcfc7e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79d9f2f4b065/disk-9f8413c4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cbc68430d9c6/vmlinux-9f8413c4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9740ad9fc172/bzImage-9f8413c4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+579eb95e588b48b4499c@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in em_ret_far+0x332/0x340 arch/x86/kvm/emulate.c:2258
 em_ret_far+0x332/0x340 arch/x86/kvm/emulate.c:2258
 em_ret_far_imm+0x39/0x4f0 arch/x86/kvm/emulate.c:2270
 x86_emulate_insn+0x1d81/0x5800 arch/x86/kvm/emulate.c:5289
 x86_emulate_instruction+0x13c5/0x3090 arch/x86/kvm/x86.c:9101
 kvm_mmu_page_fault+0x100a/0x1120 arch/x86/kvm/mmu/mmu.c:5778
 handle_ept_violation+0x4ef/0x7e0 arch/x86/kvm/vmx/vmx.c:5788
 __vmx_handle_exit arch/x86/kvm/vmx/vmx.c:6567 [inline]
 vmx_handle_exit+0x1b01/0x2130 arch/x86/kvm/vmx/vmx.c:6584
 vcpu_enter_guest arch/x86/kvm/x86.c:10992 [inline]
 vcpu_run arch/x86/kvm/x86.c:11095 [inline]
 kvm_arch_vcpu_ioctl_run+0x9d4f/0xc680 arch/x86/kvm/x86.c:11321
 kvm_vcpu_ioctl+0xbfc/0x1770 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4155
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0x225/0x410 fs/ioctl.c:857
 __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Local variable eip created at:
 em_ret_far+0x3a/0x340 arch/x86/kvm/emulate.c:2243
 em_ret_far_imm+0x39/0x4f0 arch/x86/kvm/emulate.c:2270

CPU: 0 PID: 5001 Comm: syz-executor428 Not tainted 6.7.0-syzkaller-00562-g9f8413c4a66f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.