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irq bypass consumer (token         (ptrval)) registration fails: -16
irq bypass consumer (token         (ptrval)) registration fails: -16
irq bypass consumer (token         (ptrval)) registration fails: -16
irq bypass consumer (token         (ptrval)) registration fails: -16
==================================================================
BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4b1/0x530 virt/lib/irqbypass.c:198
Read of size 8 at addr ffff8801c7026178 by task syz-executor869/4500

CPU: 0 PID: 4500 Comm: syz-executor869 Not tainted 4.17.0-rc4+ #37
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+0x1b9/0x294 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+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 irq_bypass_register_consumer+0x4b1/0x530 virt/lib/irqbypass.c:198
 kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
 kvm_irqfd+0x1599/0x1ec0 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
 kvm_vm_ioctl+0xf84/0x1d90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2997
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
 __do_sys_ioctl fs/ioctl.c:708 [inline]
 __se_sys_ioctl fs/ioctl.c:706 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445879
RSP: 002b:00007fd59da6ada8 EFLAGS: 00000297 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dac64 RCX: 0000000000445879
RDX: 0000000020018000 RSI: 000000004020ae76 RDI: 00000000000003fc
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 00000000006dac60
R13: 6d766b2f7665642f R14: 00007fd59da6b9c0 R15: 0000000000000009

Allocated by task 4500:
 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:512 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
 kvm_irqfd+0x187/0x1ec0 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
 kvm_vm_ioctl+0xf84/0x1d90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2997
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
 __do_sys_ioctl fs/ioctl.c:708 [inline]
 __se_sys_ioctl fs/ioctl.c:706 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 25:
 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+0x13a/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
 worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
 kthread+0x345/0x410 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

The buggy address belongs to the object at ffff8801c7026000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 376 bytes inside of
 512-byte region [ffff8801c7026000, ffff8801c7026200)
The buggy address belongs to the page:
page:ffffea00071c0980 count:1 mapcount:0 mapping:ffff8801c7026000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c7026000 0000000000000000 0000000100000006
raw: ffffea00071c3ca0 ffffea00071c51e0 ffff8801da800940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c7026000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c7026080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801c7026100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff8801c7026180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c7026200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================