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BUG: KASAN: use-after-free in mon_bin_vma_fault+0x378/0x400 drivers/usb/mon/mon_bin.c:1238
Read of size 8 at addr ffff8801d08edcd0 by task syz-executor0/4985

CPU: 1 PID: 4985 Comm: syz-executor0 Not tainted 4.15.0-rc4-next-20171221+ #78
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 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
 mon_bin_vma_fault+0x378/0x400 drivers/usb/mon/mon_bin.c:1238
 __do_fault+0xeb/0x30f mm/memory.c:3206
 do_read_fault mm/memory.c:3616 [inline]
 do_fault mm/memory.c:3716 [inline]
 handle_pte_fault mm/memory.c:3947 [inline]
 __handle_mm_fault+0x1d8f/0x3ce0 mm/memory.c:4071
 handle_mm_fault+0x38f/0x930 mm/memory.c:4108
 faultin_page mm/gup.c:502 [inline]
 __get_user_pages+0x50c/0x15f0 mm/gup.c:699
 populate_vma_page_range+0x20e/0x2f0 mm/gup.c:1200
 __mm_populate+0x23a/0x450 mm/gup.c:1250
 mm_populate include/linux/mm.h:2233 [inline]
 vm_mmap_pgoff+0x241/0x280 mm/util.c:338
 SYSC_mmap_pgoff mm/mmap.c:1544 [inline]
 SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1502
 SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452ac9
RSP: 002b:00007fd895701c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9
RDX: 0000000001000004 RSI: 0000000000004000 RDI: 0000000020ac6000
RBP: 000000000000039b R08: 0000000000000014 R09: 0000000000000000
R10: 0000000000008011 R11: 0000000000000212 R12: 00000000006f2728
R13: 00000000ffffffff R14: 00007fd8957026d4 R15: 0000000000000000

Allocated by task 4985:
 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
 __do_kmalloc mm/slab.c:3709 [inline]
 __kmalloc+0x162/0x760 mm/slab.c:3718
 kmalloc include/linux/slab.h:521 [inline]
 kzalloc include/linux/slab.h:705 [inline]
 mon_bin_ioctl+0x558/0xd40 drivers/usb/mon/mon_bin.c:1025
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 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 4993:
 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:3489 [inline]
 kfree+0xd6/0x260 mm/slab.c:3804
 mon_bin_ioctl+0x68d/0xd40 drivers/usb/mon/mon_bin.c:1040
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 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

The buggy address belongs to the object at ffff8801d08edcc0
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 16 bytes inside of
 256-byte region [ffff8801d08edcc0, ffff8801d08eddc0)
The buggy address belongs to the page:
page:00000000b1b46878 count:1 mapcount:0 mapping:000000007b321d03 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d08ed040 0000000000000000 000000010000000c
raw: ffffea0007423aa0 ffffea0007423ee0 ffff8801dac007c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d08edb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d08edc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d08edc80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                 ^
 ffff8801d08edd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d08edd80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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