[syzbot] KMSAN: uninit-value in kvm_cpuid

[syzbot] KMSAN: uninit-value in kvm_cpuid

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    cd2c05533838 DO-NOT-SUBMIT: kmsan: suppress a report in ke..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=11373b17300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=978f1b2d7a5aad3e
dashboard link: https://syzkaller.appspot.com/bug?extid=d6d011bc17bb751d4aa2
compiler:       clang version 14.0.0 (git@github.com:llvm/llvm-project.git 0996585c8e3b3d409494eb5f1cad714b9e1f7fb5), GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14b6c4cb300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10fdb00f300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d6d011bc17bb751d4aa2@syzkaller.appspotmail.com

L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
=====================================================
BUG: KMSAN: uninit-value in cpuid_entry2_find arch/x86/kvm/cpuid.c:68 [inline]
BUG: KMSAN: uninit-value in kvm_find_cpuid_entry arch/x86/kvm/cpuid.c:1103 [inline]
BUG: KMSAN: uninit-value in kvm_cpuid+0x456/0x28f0 arch/x86/kvm/cpuid.c:1183
 cpuid_entry2_find arch/x86/kvm/cpuid.c:68 [inline]
 kvm_find_cpuid_entry arch/x86/kvm/cpuid.c:1103 [inline]
 kvm_cpuid+0x456/0x28f0 arch/x86/kvm/cpuid.c:1183
 kvm_vcpu_reset+0x13fb/0x1c20 arch/x86/kvm/x86.c:10885
 kvm_apic_accept_events+0x58f/0x8c0 arch/x86/kvm/lapic.c:2923
 vcpu_enter_guest+0xfd2/0x6d80 arch/x86/kvm/x86.c:9534
 vcpu_run+0x7f5/0x18d0 arch/x86/kvm/x86.c:9788
 kvm_arch_vcpu_ioctl_run+0x245b/0x2d10 arch/x86/kvm/x86.c:10020
 kvm_vcpu_ioctl+0x1055/0x1e00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3749
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x2df/0x4a0 fs/ioctl.c:860
 __x64_sys_ioctl+0xd8/0x110 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Local variable ----dummy@kvm_vcpu_reset created at:
 kvm_vcpu_reset+0x1fb/0x1c20 arch/x86/kvm/x86.c:10812
 kvm_apic_accept_events+0x58f/0x8c0 arch/x86/kvm/lapic.c:2923
=====================================================
Kernel panic - not syncing: panic_on_kmsan set ...
CPU: 1 PID: 6364 Comm: syz-executor072 Tainted: G    B             5.15.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1ff/0x28e lib/dump_stack.c:106
 dump_stack+0x25/0x28 lib/dump_stack.c:113
 panic+0x44f/0xdeb kernel/panic.c:232
 kmsan_report+0x2ee/0x300 mm/kmsan/report.c:186
 __msan_warning+0xd7/0x150 mm/kmsan/instrumentation.c:208
 cpuid_entry2_find arch/x86/kvm/cpuid.c:68 [inline]
 kvm_find_cpuid_entry arch/x86/kvm/cpuid.c:1103 [inline]
 kvm_cpuid+0x456/0x28f0 arch/x86/kvm/cpuid.c:1183
 kvm_vcpu_reset+0x13fb/0x1c20 arch/x86/kvm/x86.c:10885
 kvm_apic_accept_events+0x58f/0x8c0 arch/x86/kvm/lapic.c:2923
 vcpu_enter_guest+0xfd2/0x6d80 arch/x86/kvm/x86.c:9534
 vcpu_run+0x7f5/0x18d0 arch/x86/kvm/x86.c:9788
 kvm_arch_vcpu_ioctl_run+0x245b/0x2d10 arch/x86/kvm/x86.c:10020
 kvm_vcpu_ioctl+0x1055/0x1e00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3749
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x2df/0x4a0 fs/ioctl.c:860
 __x64_sys_ioctl+0xd8/0x110 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f51eb544a19
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe2fe74dc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f51eb544a19
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 00007ffe2fe74f68
R10: 0000000000009120 R11: 0000000000000246 R12: 00007f51eb507c80
R13: 431bde82d7b634db R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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Re: [syzbot] KMSAN: uninit-value in kvm_cpuid

[Sean Christopherson]

On Thu, Sep 30, 2021, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    cd2c05533838 DO-NOT-SUBMIT: kmsan: suppress a report in ke..
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=11373b17300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=978f1b2d7a5aad3e
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6d011bc17bb751d4aa2
> compiler:       clang version 14.0.0 (git@github.com:llvm/llvm-project.git 0996585c8e3b3d409494eb5f1cad714b9e1f7fb5), GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14b6c4cb300000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10fdb00f300000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d6d011bc17bb751d4aa2@syzkaller.appspotmail.com

#syz fix: KVM: x86: Swap order of CPUID entry "index" vs. "significant flag" checks