Hello, The following program triggers use-after-free in complete_emulated_mmio: https://gist.githubusercontent.com/dvyukov/79c7ee10f568b0d5c33788534bb6edc9/raw/2c2d4ce0fe86398ed81e65281e8c215c7c3632fb/gistfile1.txt BUG: KASAN: use-after-free in complete_emulated_mmio+0x8dd/0xb70 arch/x86/kvm/x86.c:7052 at addr ffff880069f1ed48 Read of size 8 by task syz-executor/31542 CPU: 3 PID: 31542 Comm: syz-executor Not tainted 4.9.0+ #105 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: check_memory_region+0x139/0x190 mm/kasan/kasan.c:322 memcpy+0x23/0x50 mm/kasan/kasan.c:357 complete_emulated_mmio+0x8dd/0xb70 arch/x86/kvm/x86.c:7052 kvm_arch_vcpu_ioctl_run+0x308d/0x45f0 arch/x86/kvm/x86.c:7090 kvm_vcpu_ioctl+0x673/0x1120 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2569 vfs_ioctl fs/ioctl.c:43 [inline] do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:683 SYSC_ioctl fs/ioctl.c:698 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689 entry_SYSCALL_64_fastpath+0x1f/0xc2 RIP: 0033:0x4421e9 RSP: 002b:00007f320dc67b58 EFLAGS: 00000286 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000018 RCX: 00000000004421e9 RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000018 RBP: 00000000006dbb20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000700000 R13: 00007f320de671c8 R14: 00007f320de69000 R15: 0000000000000000 Object at ffff880069f183c0, in cache kmalloc-16384 size: 16384 Allocated: PID = 31567 [<ffffffff8123eb36>] save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 [<ffffffff81943353>] save_stack+0x43/0xd0 mm/kasan/kasan.c:502 [<ffffffff8194361a>] set_track mm/kasan/kasan.c:514 [inline] [<ffffffff8194361a>] kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:605 [<ffffffff8193fa7c>] kmem_cache_alloc_trace+0xec/0x640 mm/slab.c:3629 [<ffffffff810724ce>] kvm_arch_alloc_vm include/linux/slab.h:490 [inline] [<ffffffff810724ce>] kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:613 [inline] [<ffffffff810724ce>] kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:3174 [inline] [<ffffffff810724ce>] kvm_dev_ioctl+0x1be/0x11b0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3218 [<ffffffff819af76f>] vfs_ioctl fs/ioctl.c:43 [inline] [<ffffffff819af76f>] do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:683 [<ffffffff819b0dbf>] SYSC_ioctl fs/ioctl.c:698 [inline] [<ffffffff819b0dbf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689 [<ffffffff83fd1d81>] entry_SYSCALL_64_fastpath+0x1f/0xc2 Memory state around the buggy address: ffff880069f1ec00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff880069f1ec80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff880069f1ed00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff880069f1ed80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff880069f1ee00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== On commit e93b1cc8a8965da137ffea0b88e5f62fa1d2a9e6 (Dec 19). I've also printed some values when the bug happens: pr_err("vcpu=%p, mmio_fragments=%p frag=%p frag=%d/%d len=%d gpa=%p write=%d\n", vcpu, vcpu->mmio_fragments, frag, vcpu->mmio_cur_fragment, vcpu->mmio_nr_fragments, frag->len, (void*)frag->gpa, vcpu->mmio_is_write); [ 26.765898] vcpu=ffff880068590100, mmio_fragments=ffff880068590338 frag=ffff880068590338 frag=0/1 len=152 gpa=0000000000001008 write=1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
