bisecting fixing commit since b94de4d19498b454645b72d08a05d32fa9074fb5 building syzkaller on cba33199be220cbf61f7c0c8223d88a25a913d6f testing commit b94de4d19498b454645b72d08a05d32fa9074fb5 with gcc (GCC) 8.1.0 kernel signature: 10948e6ae50ebb52f1730c72a86f9055fe403a35d1e2cf5e9c06fcaa8db4b043 all runs: crashed: KASAN: use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio testing current HEAD daefdc9eb24bfa11ab77a4b2a9c3923f1051fe0b testing commit daefdc9eb24bfa11ab77a4b2a9c3923f1051fe0b with gcc (GCC) 8.1.0 kernel signature: 3c46063eca01bad3e7c2d09a2a7eae64c058e165b9d09f02c70c9f966c1df326 all runs: crashed: KASAN: use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio revisions tested: 2, total time: 25m51.996145075s (build: 19m30.316010805s, test: 5m52.707884317s) the crash still happens on HEAD commit msg: Linux 4.19.161 crash: KASAN: use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready kvm: failed to shrink bus, removing it completely IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready ================================================================== 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 ffff8881d121a600 by task syz-executor.2/9232 CPU: 1 PID: 9232 Comm: syz-executor.2 Not tainted 4.19.161-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+0x17c/0x22a lib/dump_stack.c:118 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0x242/0x307 mm/kasan/report.c:412 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 kvm_vm_ioctl_unregister_coalesced_mmio+0x1f2/0x2a0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:178 kvm_vm_ioctl+0x5ac/0x1770 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3252 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45deb9 Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fb91372ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000012740 RCX: 000000000045deb9 RDX: 0000000020000180 RSI: 000000004010ae68 RDI: 0000000000000004 RBP: 00007fb91372aca0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe535e63ff R14: 00007fb91372b9c0 R15: 000000000118bf2c Allocated by task 9232: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538 kmem_cache_alloc_trace+0x152/0x3a0 mm/slab.c:3625 kmalloc include/linux/slab.h:515 [inline] kzalloc include/linux/slab.h:709 [inline] kvm_vm_ioctl_register_coalesced_mmio+0x4f/0x320 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:146 kvm_vm_ioctl+0xa0e/0x1770 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3243 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 9232: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x13c/0x220 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kfree+0xcf/0x220 mm/slab.c:3822 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.38+0xbd/0x10e arch/x86/kvm/../../../virt/kvm/kvm_main.c:3875 kvm_vm_ioctl_unregister_coalesced_mmio+0x15b/0x2a0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:180 kvm_vm_ioctl+0x5ac/0x1770 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3252 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff8881d121a600 which belongs to the cache kmalloc-64 of size 64 The buggy address is located 0 bytes inside of 64-byte region [ffff8881d121a600, ffff8881d121a640) The buggy address belongs to the page: page:ffffea0007448680 count:1 mapcount:0 mapping:ffff8881f6000340 index:0x0 flags: 0x17ff00000000100(slab) raw: 017ff00000000100 ffffea0007b6df48 ffffea0007b28208 ffff8881f6000340 raw: 0000000000000000 ffff8881d121a000 0000000100000020 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8881d121a500: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ffff8881d121a580: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc >ffff8881d121a600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ^ ffff8881d121a680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ffff8881d121a700: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ================================================================== wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 0 wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50 wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50 wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 0 IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready CPU: 0 PID: 9308 Comm: syz-executor.1 Tainted: G B 4.19.161-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+0x17c/0x22a lib/dump_stack.c:118 fail_dump lib/fault-inject.c:51 [inline] should_fail.cold.2+0x5/0xb lib/fault-inject.c:149 __should_failslab+0xba/0xf0 mm/failslab.c:32 should_failslab+0x9/0x14 mm/slab_common.c:1588 slab_pre_alloc_hook mm/slab.h:424 [inline] slab_alloc mm/slab.c:3383 [inline] __do_kmalloc mm/slab.c:3725 [inline] __kmalloc+0x2b5/0x3d0 mm/slab.c:3736 kmalloc include/linux/slab.h:520 [inline] kvm_io_bus_unregister_dev+0x116/0x2f0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3863 kvm_vm_ioctl_unregister_coalesced_mmio+0x15b/0x2a0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:180 kvm_vm_ioctl+0x5ac/0x1770 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3252 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45deb9 Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ff832fd1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000012740 RCX: 000000000045deb9 RDX: 0000000020000180 RSI: 000000004010ae68 RDI: 0000000000000004 RBP: 00007ff832fd1ca0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffdcc08998f R14: 00007ff832fd29c0 R15: 000000000118bf2c CPU: 1 PID: 9291 Comm: syz-executor.3 Tainted: G B 4.19.161-syzkaller #0 IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready 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+0x17c/0x22a lib/dump_stack.c:118 fail_dump lib/fault-inject.c:51 [inline] should_fail.cold.2+0x5/0xb lib/fault-inject.c:149 IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready __should_failslab+0xba/0xf0 mm/failslab.c:32 should_failslab+0x9/0x14 mm/slab_common.c:1588 slab_pre_alloc_hook mm/slab.h:424 [inline] slab_alloc mm/slab.c:3383 [inline] __do_kmalloc mm/slab.c:3725 [inline] __kmalloc+0x2b5/0x3d0 mm/slab.c:3736 kmalloc include/linux/slab.h:520 [inline] kvm_io_bus_unregister_dev+0x116/0x2f0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3863