syzbot

==================================================================
BUG: KASAN: use-after-free in kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:412 [inline]
BUG: KASAN: use-after-free in kvm_irqfd+0x1c48/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
Read of size 8 at addr ffff880039a6c390 by task syz-executor5/6403

CPU: 1 PID: 6403 Comm: syz-executor5 Not tainted 4.13.0-rc7-next-20170901+ #13
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 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+0x24e/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:412 [inline]
 kvm_irqfd+0x1c48/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
 kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3032
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x447299
RSP: 002b:00007f2afe016c08 EFLAGS: 00000296 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000018 RCX: 0000000000447299
RDX: 000000002004ffe0 RSI: 000000004020ae76 RDI: 0000000000000018
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000296 R12: 00000000ffffffff
R13: 0000000000003c30 R14: 00000000006e6cf0 R15: 0000000020036000

Allocated by task 6403:
 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:3032
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 801:
 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 ffff880039a6c280
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 272 bytes inside of
 512-byte region [ffff880039a6c280, ffff880039a6c480)
The buggy address belongs to the page:
page:ffffea0000e69b00 count:1 mapcount:0 mapping:ffff880039a6c000 index:0xffff880039a6ca00
flags: 0x100000000000100(slab)
raw: 0100000000000100 ffff880039a6c000 ffff880039a6ca00 0000000100000005
raw: ffffea0000f40660 ffffea0000e4dc60 ffff88003e800940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff880039a6c280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff880039a6c300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff880039a6c380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff880039a6c400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff880039a6c480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================