Re: [syzbot] [kvm?] KASAN: slab-use-after-free Read in kvm_tdp_mmu_invalidate_all_roots

[Sean Christopherson]

On Sun, Apr 23, 2023, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    d3e1ee0e67e7 Add linux-next specific files for 20230421
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=118a0520280000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=53c789efbcc06cf6
> dashboard link: https://syzkaller.appspot.com/bug?extid=864ac0b626794668b732
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/c558a9e1fe6a/disk-d3e1ee0e.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/2ec100a34c4c/vmlinux-d3e1ee0e.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/1afcd9936dc1/bzImage-d3e1ee0e.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+864ac0b626794668b732@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ==================================================================
> BUG: KASAN: slab-use-after-free in kvm_tdp_mmu_invalidate_all_roots+0x2e3/0x370 arch/x86/kvm/mmu/tdp_mmu.c:945
> Read of size 8 at addr ffff88807c27d528 by task syz-executor.2/5817
> 
> CPU: 0 PID: 5817 Comm: syz-executor.2 Not tainted 6.3.0-rc7-next-20230421-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
>  print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
>  print_report mm/kasan/report.c:462 [inline]
>  kasan_report+0x11c/0x130 mm/kasan/report.c:572
>  kvm_tdp_mmu_invalidate_all_roots+0x2e3/0x370 arch/x86/kvm/mmu/tdp_mmu.c:945
>  kvm_mmu_uninit_tdp_mmu+0x16/0x100 arch/x86/kvm/mmu/tdp_mmu.c:48
>  kvm_mmu_uninit_vm+0x6a/0x70 arch/x86/kvm/mmu/mmu.c:6239
>  kvm_arch_destroy_vm+0x369/0x490 arch/x86/kvm/x86.c:12465
>  kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1313 [inline]
>  kvm_put_kvm+0x4da/0xae0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1347
>  kvm_vcpu_release+0x51/0x70 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3846
>  __fput+0x27c/0xa90 fs/file_table.c:321
>  task_work_run+0x16f/0x270 kernel/task_work.c:179
>  resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
>  exit_to_user_mode_prepare+0x210/0x240 kernel/entry/common.c:204
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
>  syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297
>  do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f426b83e01b
> Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
> RSP: 002b:00007ffe38a35070 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000008 RCX: 00007f426b83e01b
> RDX: 0000000000000000 RSI: 0000001b32b3a7d4 RDI: 0000000000000007
> RBP: 00007f426b9ad980 R08: 0000000000000000 R09: 0000000075ee794b
> R10: 0000000000000000 R11: 0000000000000293 R12: 000000000003d553
> R13: 00007ffe38a35170 R14: 00007ffe38a35190 R15: 0000000000000032
>  </TASK>

#syz fix: KVM: x86: Preserve TDP MMU roots until they are explicitly invalidated