bisecting fixing commit since 5b7a52cd2eef952cee8a72512ef370bcdef46636 building syzkaller on a1839e81524f4e427a4b57bca0e4633d459d3d18 testing commit 5b7a52cd2eef952cee8a72512ef370bcdef46636 with gcc (GCC) 8.1.0 kernel signature: b3e8dfe92bb880a16fbfd0cad6e52aeacd87c8e1958b5ff3c84575ade782012b all runs: crashed: KASAN: use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio testing current HEAD c196b3a9c83ae3491280b739d231d02b3cb9d041 testing commit c196b3a9c83ae3491280b739d231d02b3cb9d041 with gcc (GCC) 8.1.0 kernel signature: b449075add52da42d4e0beef43e7f8e85872721a31878c6347f53bdca6318771 all runs: crashed: KASAN: use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio revisions tested: 2, total time: 30m14.185800164s (build: 23m52.885475933s, test: 5m41.888281578s) the crash still happens on HEAD commit msg: Linux 4.14.210 crash: KASAN: use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio kvm: failed to shrink bus, removing it completely batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 ================================================================== batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! BUG: KASAN: use-after-free in kvm_vm_ioctl_unregister_coalesced_mmio+0x1f2/0x2a0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:178 Read of size 8 at addr ffff8881f407ad00 by task syz-executor.1/9071 CPU: 0 PID: 9071 Comm: syz-executor.1 Not tainted 4.14.210-syzkaller #0 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x14b/0x1f1 lib/dump_stack.c:58 print_address_description.cold.6+0x9/0x1ca mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report.cold.7+0x11a/0x2d4 mm/kasan/report.c:409 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430 kvm_vm_ioctl_unregister_coalesced_mmio+0x1f2/0x2a0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:178 kvm_vm_ioctl+0x57b/0x19a0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3096 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45de59 RSP: 002b:00007f9906916c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000000126c0 RCX: 000000000045de59 RDX: 0000000020000180 RSI: 000000004010ae68 RDI: 0000000000000006 RBP: 00007f9906916ca0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fff909c99df R14: 00007f99069179c0 R15: 000000000118bf2c Allocated by task 9071: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! save_stack mm/kasan/kasan.c:447 [inline] set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:551 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:536 kmem_cache_alloc_trace+0x152/0x3f0 mm/slab.c:3618 kmalloc include/linux/slab.h:488 [inline] kzalloc include/linux/slab.h:661 [inline] kvm_vm_ioctl_register_coalesced_mmio+0x4f/0x320 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:146 kvm_vm_ioctl+0x4c2/0x19a0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3087 IPv6: ADDRCONF(NETDEV_UP): batadv_slave_1: link is not ready vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb batman_adv: batadv0: Interface activated: batadv_slave_1 Freed by task 9071: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack mm/kasan/kasan.c:447 [inline] set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0xab/0x190 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 coalesced_mmio_destructor+0x100/0x150 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:101 kvm_iodevice_destructor include/kvm/iodev.h:73 [inline] kvm_io_bus_unregister_dev.cold.30+0xbd/0x113 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3719 kvm_vm_ioctl_unregister_coalesced_mmio+0x15b/0x2a0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:180 kvm_vm_ioctl+0x57b/0x19a0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3096 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb The buggy address belongs to the object at ffff8881f407ad00 which belongs to the cache kmalloc-64 of size 64 The buggy address is located 0 bytes inside of 64-byte region [ffff8881f407ad00, ffff8881f407ad40) The buggy address belongs to the page: page:ffffea0007d01e80 count:1 mapcount:0 mapping:ffff8881f407a000 index:0x0 flags: 0x17ff00000000100(slab) raw: 017ff00000000100 ffff8881f407a000 0000000000000000 0000000100000020 raw: ffffea0007bc42a0 ffffea0007b7e560 ffff8881f6000340 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8881f407ac00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ffff8881f407ac80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >ffff8881f407ad00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ^ ffff8881f407ad80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff8881f407ae00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ================================================================== ieee80211 phy6: hwaddr 02:00:00:00:06:00 registered batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0