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

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Message-ID: <ZdYBBPypcFATU8c5@google.com>
Date: Wed, 21 Feb 2024 05:56:20 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: syzbot <syzbot+c9aca2253922f806a75a@...kaller.appspotmail.com>
Cc: bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, mingo@...hat.com, 
	pbonzini@...hat.com, syzkaller-bugs@...glegroups.com, tglx@...utronix.de, 
	x86@...nel.org
Subject: Re: [syzbot] [kvm?] KMSAN: uninit-value in em_ret_near_imm

On Tue, Feb 20, 2024, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    0f1dd5e91e2b Merge tag 'sound-6.8-rc5' of git://git.kernel..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17bec778180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e3dd779fba027968
> dashboard link: https://syzkaller.appspot.com/bug?extid=c9aca2253922f806a75a
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/b6e52e101a62/disk-0f1dd5e9.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/64025c9168bf/vmlinux-0f1dd5e9.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/491e1a922dc9/bzImage-0f1dd5e9.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c9aca2253922f806a75a@...kaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in assign_eip_near arch/x86/kvm/emulate.c:829 [inline]
> BUG: KMSAN: uninit-value in em_ret_near_imm+0x13c/0x580 arch/x86/kvm/emulate.c:3192
>  assign_eip_near arch/x86/kvm/emulate.c:829 [inline]
>  em_ret_near_imm+0x13c/0x580 arch/x86/kvm/emulate.c:3192
>  x86_emulate_insn+0x1d87/0x5880 arch/x86/kvm/emulate.c:5292
>  x86_emulate_instruction+0x13c9/0x30a0 arch/x86/kvm/x86.c:9175
>  kvm_emulate_instruction arch/x86/kvm/x86.c:9255 [inline]
>  complete_emulated_io arch/x86/kvm/x86.c:11212 [inline]
>  complete_emulated_mmio+0x70b/0x8b0 arch/x86/kvm/x86.c:11272
>  kvm_arch_vcpu_ioctl_run+0x1837/0xb890 arch/x86/kvm/x86.c:11384
>  kvm_vcpu_ioctl+0xbfc/0x1770 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4441
>  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+0xcf/0x1e0 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> 
> Local variable eip created at:
>  em_ret_near_imm+0x3a/0x580 arch/x86/kvm/emulate.c:3189
>  x86_emulate_insn+0x1d87/0x5880 arch/x86/kvm/emulate.c:5292
> 
> CPU: 0 PID: 6232 Comm: syz-executor.3 Not tainted 6.8.0-rc4-syzkaller-00267-g0f1dd5e91e2b #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
> =====================================================

#syz fix: KVM: x86: Clean up partially uninitialized integer in emulate_pop()