[syzbot] [kvm?] KMSAN: uninit-value in em_ret_near_imm

[syzbot <syzbot+c9aca2253922f806a75a@syzkaller.appspotmail.com>]

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@syzkaller.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
=====================================================


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