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BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4f0/0x500 virt/lib/irqbypass.c:198
Read of size 8 at addr ffff8801d90e4190 by task syz-executor0/3901

CPU: 0 PID: 3901 Comm: syz-executor0 Not tainted 4.14.0-rc2+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 irq_bypass_register_consumer+0x4f0/0x500 virt/lib/irqbypass.c:198
 kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
 kvm_irqfd+0x137a/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
 kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2991
 kvm_vm_compat_ioctl+0x2ed/0x3e0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3135
 C_SYSC_ioctl fs/compat_ioctl.c:1593 [inline]
 compat_SyS_ioctl+0x1d7/0x3290 fs/compat_ioctl.c:1540
 do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
 do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124
RIP: 0023:0xf7f1bc79
RSP: 002b:00000000f7f1705c EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000013 RCX: 000000004020ae76
RDX: 0000000020025fe0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3901:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3627
 kmalloc include/linux/slab.h:493 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
 kvm_irqfd+0x16c/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
 kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2991
 kvm_vm_compat_ioctl+0x2ed/0x3e0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3135
 C_SYSC_ioctl fs/compat_ioctl.c:1593 [inline]
 compat_SyS_ioctl+0x1d7/0x3290 fs/compat_ioctl.c:1540
 do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
 do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124

Freed by task 23:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xca/0x250 mm/slab.c:3820
 irqfd_shutdown+0x13c/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
 process_one_work+0xbfa/0x1bd0 kernel/workqueue.c:2119
 worker_thread+0x223/0x1860 kernel/workqueue.c:2253
 kthread+0x39c/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

The buggy address belongs to the object at ffff8801d90e4000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff8801d90e4000, ffff8801d90e4200)
The buggy address belongs to the page:
page:ffffea0007643900 count:1 mapcount:0 mapping:ffff8801d90e4000 index:0x0
flags: 0x200000000000100(slab)
raw: 0200000000000100 ffff8801d90e4000 0000000000000000 0000000100000006
raw: ffffea000764a3a0 ffffea0007622b60 ffff8801dac00940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d90e4080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d90e4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d90e4180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8801d90e4200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d90e4280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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