Date:   Mon, 17 Aug 2020 11:02:25 -0700
From:   syzbot <syzbot+47665dbce263479409c8@...kaller.appspotmail.com>
To:     bp@...en8.de, hpa@...or.com, jmattson@...gle.com, joro@...tes.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, syzkaller-bugs@...glegroups.com,
        tglx@...utronix.de, vkuznets@...hat.com, wanpengli@...cent.com,
        x86@...nel.org
Subject: KASAN: use-after-free Write in paging32_walk_addr_generic

Hello,

syzbot found the following issue on:

HEAD commit:    9123e3a7 Linux 5.9-rc1
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1355e34a900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3d400a47d1416652
dashboard link: https://syzkaller.appspot.com/bug?extid=47665dbce263479409c8
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11e059f6900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=170f8ab4900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+47665dbce263479409c8@...kaller.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: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in paging32_cmpxchg_gpte arch/x86/kvm/mmu/paging_tmpl.h:181 [inline]
BUG: KASAN: use-after-free in paging32_update_accessed_dirty_bits arch/x86/kvm/mmu/paging_tmpl.h:287 [inline]
BUG: KASAN: use-after-free in paging32_walk_addr_generic+0x155d/0x1980 arch/x86/kvm/mmu/paging_tmpl.h:457
Write of size 4 at addr ffff888000105000 by task syz-executor735/6849

CPU: 1 PID: 6849 Comm: syz-executor735 Not tainted 5.9.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 instrument_atomic_write include/linux/instrumented.h:71 [inline]
 paging32_cmpxchg_gpte arch/x86/kvm/mmu/paging_tmpl.h:181 [inline]
 paging32_update_accessed_dirty_bits arch/x86/kvm/mmu/paging_tmpl.h:287 [inline]
 paging32_walk_addr_generic+0x155d/0x1980 arch/x86/kvm/mmu/paging_tmpl.h:457
 paging32_walk_addr arch/x86/kvm/mmu/paging_tmpl.h:514 [inline]
 paging32_gva_to_gpa+0xb2/0x1d0 arch/x86/kvm/mmu/paging_tmpl.h:958
 vcpu_mmio_gva_to_gpa arch/x86/kvm/x86.c:5758 [inline]
 emulator_read_write_onepage+0x2f3/0xa70 arch/x86/kvm/x86.c:5874
 emulator_read_write+0x1c4/0x5a0 arch/x86/kvm/x86.c:5934
 emulator_write_emulated arch/x86/kvm/x86.c:5971 [inline]
 emulator_fix_hypercall+0x132/0x190 arch/x86/kvm/x86.c:7763
 em_hypercall+0x5d/0x130 arch/x86/kvm/emulate.c:3803
 x86_emulate_insn+0x5e8/0x3d20 arch/x86/kvm/emulate.c:5676
 x86_emulate_instruction+0x752/0x1e00 arch/x86/kvm/x86.c:7017
 kvm_emulate_instruction arch/x86/kvm/x86.c:7085 [inline]
 handle_ud+0xa8/0x240 arch/x86/kvm/x86.c:5718
 handle_exception_nmi+0xaf7/0x1270 arch/x86/kvm/vmx/vmx.c:4761
 vmx_handle_exit+0x293/0x14c0 arch/x86/kvm/vmx/vmx.c:6118
 vcpu_enter_guest+0x14d6/0x3b60 arch/x86/kvm/x86.c:8641
 vcpu_run arch/x86/kvm/x86.c:8706 [inline]
 kvm_arch_vcpu_ioctl_run+0x440/0x1780 arch/x86/kvm/x86.c:8923
 kvm_vcpu_ioctl+0x467/0xdf0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3229
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x443639
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 0f 83 9b 0b fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffcf07dea38 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcf07dea40 RCX: 0000000000443639
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006
RBP: 0000000000000000 R08: 0000000000000000 R09: 00000000004011b0
R10: 0000000000000012 R11: 0000000000000246 R12: 0000000000404660
R13: 00000000004046f0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:000000000c451483 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x105
flags: 0x7ffe0000000000()
raw: 007ffe0000000000 ffffea0000004148 ffffea0000004148 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888000104f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888000104f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888000105000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888000105080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888000105100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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