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BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4e1/0x550 virt/lib/irqbypass.c:198
Read of size 8 at addr ffff88019f1439b8 by task syz-executor2/24045

CPU: 0 PID: 24045 Comm: syz-executor2 Not tainted 4.18.0-rc3-next-20180706+ #1
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+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 irq_bypass_register_consumer+0x4e1/0x550 virt/lib/irqbypass.c:198
 kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
 kvm_irqfd+0x198e/0x1ef0 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
 kvm_vm_ioctl+0xf80/0x1d80 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3015
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
 __do_sys_ioctl fs/ioctl.c:709 [inline]
 __se_sys_ioctl fs/ioctl.c:707 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455ba9
Code: 1d ba 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 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007ff0e04c5c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff0e04c66d4 RCX: 0000000000455ba9
RDX: 0000000020000180 RSI: 000000004020ae76 RDI: 000000000000001b
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004bdca1 R14: 00000000004cc220 R15: 0000000000000000

Allocated by task 24045:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
 kmalloc include/linux/slab.h:513 [inline]
 kzalloc include/linux/slab.h:707 [inline]
 kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
 kvm_irqfd+0x18f/0x1ef0 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
 kvm_vm_ioctl+0xf80/0x1d80 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3015
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
 __do_sys_ioctl fs/ioctl.c:709 [inline]
 __se_sys_ioctl fs/ioctl.c:707 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4500:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xd9/0x260 mm/slab.c:3813
 irqfd_shutdown+0x144/0x1c0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
 process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
 worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415

The buggy address belongs to the object at ffff88019f143840
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 376 bytes inside of
 512-byte region [ffff88019f143840, ffff88019f143a40)
The buggy address belongs to the page:
page:ffffea00067c50c0 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006b91dc8 ffffea0007260c08 ffff8801da800940
raw: 0000000000000000 ffff88019f1430c0 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88019f143880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88019f143900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88019f143980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff88019f143a00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88019f143a80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
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