BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4f0/0x500 virt/lib/irqbypass.c:198
Read of size 8 at addr ffff88007a120c50 by task syz-executor2/3570

CPU: 3 PID: 3570 Comm: syz-executor2 Not tainted 4.14.0-rc8-next-20171110+ #12
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 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:2988
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x447c99
RSP: 002b:00007ff23cb21bd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff23cb226cc RCX: 0000000000447c99
RDX: 0000000020227000 RSI: 000000004020ae76 RDI: 0000000000000008
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000008568 R14: 00000000006ec608 R15: 00007ff23cb22700

Allocated by task 3570:
 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:3614
 kmalloc include/linux/slab.h:514 [inline]
 kzalloc include/linux/slab.h:703 [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:2988
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 1216:
 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:3492 [inline]
 kfree+0xca/0x250 mm/slab.c:3807
 irqfd_shutdown+0x13c/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
 process_one_work+0xbfa/0x1bc0 kernel/workqueue.c:2112
 worker_thread+0x223/0x1990 kernel/workqueue.c:2246
 kthread+0x37a/0x440 kernel/kthread.c:238
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:437

The buggy address belongs to the object at ffff88007a120ac0
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff88007a120ac0, ffff88007a120cc0)
The buggy address belongs to the page:
page:ffffea0001e84800 count:1 mapcount:0 mapping:ffff88007a1200c0 index:0x0
flags: 0x500000000000100(slab)
raw: 0500000000000100 ffff88007a1200c0 0000000000000000 0000000100000006
raw: ffffea0001e823e0 ffffea0001ea0de0 ffff88002dc00940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88007a120b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88007a120b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88007a120c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88007a120c80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88007a120d00: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
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