BUG: KASAN: use-after-free in free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116
Read of size 4 at addr ffff88006d2cb7c8 by task kworker/u9:0/3710

CPU: 1 PID: 3710 Comm: kworker/u9:0 Not tainted 4.13.0-rc4-next-20170811 #2
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_load4_noabort+0x14/0x20 mm/kasan/report.c:429
 free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116
 free_ldt_struct arch/x86/kernel/ldt.c:173 [inline]
 destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171
 destroy_context arch/x86/include/asm/mmu_context.h:157 [inline]
 __mmdrop+0xe9/0x530 kernel/fork.c:889
 mmdrop include/linux/sched/mm.h:42 [inline]
 exec_mmap fs/exec.c:1061 [inline]
 flush_old_exec+0x173c/0x1ff0 fs/exec.c:1291
 load_elf_binary+0x81f/0x4ba0 fs/binfmt_elf.c:855
 search_binary_handler+0x142/0x6b0 fs/exec.c:1652
 exec_binprm fs/exec.c:1694 [inline]
 do_execveat_common.isra.33+0x1746/0x22e0 fs/exec.c:1816
 do_execve+0x31/0x40 fs/exec.c:1860
 call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Allocated by task 3700:
 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]
 alloc_ldt_struct+0x52/0x140 arch/x86/kernel/ldt.c:67
 write_ldt+0x7b7/0xab0 arch/x86/kernel/ldt.c:277
 sys_modify_ldt+0x1ef/0x240 arch/x86/kernel/ldt.c:307
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 3700:
 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
 free_ldt_struct.part.2+0xdd/0x150 arch/x86/kernel/ldt.c:121
 free_ldt_struct arch/x86/kernel/ldt.c:173 [inline]
 destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171
 destroy_context arch/x86/include/asm/mmu_context.h:157 [inline]
 __mmdrop+0xe9/0x530 kernel/fork.c:889
 mmdrop include/linux/sched/mm.h:42 [inline]
 __mmput kernel/fork.c:916 [inline]
 mmput+0x541/0x6e0 kernel/fork.c:927
 copy_process.part.36+0x22e1/0x4af0 kernel/fork.c:1931
 copy_process kernel/fork.c:1546 [inline]
 _do_fork+0x1ef/0xfb0 kernel/fork.c:2025
 SYSC_clone kernel/fork.c:2135 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2129
 do_syscall_64+0x26c/0x8c0 arch/x86/entry/common.c:287
 return_from_SYSCALL_64+0x0/0x7a

The buggy address belongs to the object at ffff88006d2cb7c0
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 8 bytes inside of
 32-byte region [ffff88006d2cb7c0, ffff88006d2cb7e0)
The buggy address belongs to the page:
page:ffffea0001b4b2c0 count:1 mapcount:0 mapping:ffff88006d2cb000 index:0xffff88006d2cbfc1
flags: 0x500000000000100(slab)
raw: 0500000000000100 ffff88006d2cb000 ffff88006d2cbfc1 0000000100000027
raw: ffffea0001b33b20 ffffea0001b38520 ffff88003e8001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88006d2cb680: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff88006d2cb700: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff88006d2cb780: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
                                              ^
 ffff88006d2cb800: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff88006d2cb880: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
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