On Fri, 21 Apr 2023 at 23:52, 'Sean Christopherson' via syzkaller-bugs <syzkaller-bugs@xxxxxxxxxxxxxxxx> wrote: > > On Fri, Apr 21, 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=16ac3de0280000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=53c789efbcc06cf6 > > dashboard link: https://syzkaller.appspot.com/bug?extid=094a74444165dbcd3a54 > > 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+094a74444165dbcd3a54@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ------------[ cut here ]------------ > > WARNING: CPU: 0 PID: 12623 at arch/x86/kvm/mmu/tdp_mmu.c:943 kvm_tdp_mmu_invalidate_all_roots+0x2bd/0x370 arch/x86/kvm/mmu/tdp_mmu.c:943 > > Modules linked in: > > CPU: 0 PID: 12623 Comm: syz-executor.3 Not tainted 6.3.0-rc7-next-20230421-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023 > > RIP: 0010:kvm_tdp_mmu_invalidate_all_roots+0x2bd/0x370 arch/x86/kvm/mmu/tdp_mmu.c:943 > > Call Trace: > > <TASK> > > 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_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1245 [inline] > > kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:5017 [inline] > > kvm_dev_ioctl+0x11be/0x1bb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:5059 > > vfs_ioctl fs/ioctl.c:51 [inline] > > __do_sys_ioctl fs/ioctl.c:870 [inline] > > __se_sys_ioctl fs/ioctl.c:856 [inline] > > __x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Gah, kvm->users_count is elevated when the VM is destroyed if creation fails, > but mmu_lock isn't held in that case, and lockdep yells. This particular bug is > effectively a false positive, nothing else holds a reference to the VM. > > However, syzbot found another bug that _is_ a real problem (hasn't been reported > upstream yet for whatever reason). It was staged in the moderation queue for manual moderation: https://github.com/google/syzkaller/blob/master/docs/syzbot.md#moderation-queue here: https://groups.google.com/g/syzkaller-upstream-moderation/c/pTGA87FeSIE I've pushed it upstream since you say it's worth fixing. > Not holding mmu_lock during "real" VM destruction > is problematic because walking the list can race with the asynchronous worker > deleting and freeing from the list. > > Posted a fixed version[*] that should resolve both issues by protecting the walk > with RCU. > > [*] https://lore.kernel.org/all/20230421214946.2571580-1-seanjc@xxxxxxxxxx > > ================================================================== > 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 ffff88801c8cf948 by task syz-executor.1/17012 > > CPU: 0 PID: 17012 Comm: syz-executor.1 Not tainted 6.3.0-rc7-next-20230421-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023 > 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: 0033:0x7fd7a583e01b > 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:00007ffc821a2fb0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 > RAX: 0000000000000000 RBX: 000000000000000a RCX: 00007fd7a583e01b > RDX: 0000000000000000 RSI: 00007fd7a5400000 RDI: 0000000000000009 > RBP: 00007fd7a59ad980 R08: 0000000000000000 R09: 0000000071612a4e > R10: 0000000000000000 R11: 0000000000000293 R12: 000000000014ffb4 > R13: 00007ffc821a30b0 R14: 00007fd7a59ac050 R15: 0000000000000032 > </TASK> > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/ZEMFpqxvOHd2kZiu%40google.com.
