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 ffff88003d56d488 by task syz-executor7/3261

CPU: 3 PID: 3261 Comm: syz-executor7 Not tainted 4.13.0-rc5-next-20170815+ #3
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]
 finish_task_switch+0x456/0x740 kernel/sched/core.c:2658
 context_switch kernel/sched/core.c:2789 [inline]
 __schedule+0x8f0/0x2070 kernel/sched/core.c:3362
 schedule+0x108/0x440 kernel/sched/core.c:3421
 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3479
 __mutex_lock_common kernel/locking/mutex.c:833 [inline]
 __mutex_lock+0xadf/0x1870 kernel/locking/mutex.c:893
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
 perf_trace_init+0x58/0xab0 kernel/trace/trace_event_perf.c:216
 perf_tp_event_init+0x7d/0xf0 kernel/events/core.c:7981
 perf_try_init_event+0xc9/0x1f0 kernel/events/core.c:9205
 perf_init_event kernel/events/core.c:9243 [inline]
 perf_event_alloc+0x1c5b/0x2a00 kernel/events/core.c:9502
 SYSC_perf_event_open+0x7f3/0x2d90 kernel/events/core.c:9950
 SyS_perf_event_open+0x39/0x50 kernel/events/core.c:9841
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x446739
RSP: 002b:00007efecf972c08 EFLAGS: 00000286 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 000000002047f000 RCX: 0000000000446739
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 000000002047f000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000286 R12: 0000000000000000
R13: 0000000000000000 R14: 00007efecf9739c0 R15: 00007efecf973700

Allocated by task 3206:
 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 3206:
 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 ffff88003d56d480
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 8 bytes inside of
 32-byte region [ffff88003d56d480, ffff88003d56d4a0)
The buggy address belongs to the page:
page:ffffea0000f55b40 count:1 mapcount:0 mapping:ffff88003d56d000 index:0xffff88003d56dfc1
flags: 0x100000000000100(slab)
raw: 0100000000000100 ffff88003d56d000 ffff88003d56dfc1 0000000100000039
raw: ffffea0000ef9ee0 ffffea0000f55860 ffff88003e8001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88003d56d380: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff88003d56d400: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff88003d56d480: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
                      ^
 ffff88003d56d500: fb fb fb fb fc fc fc fc 00 01 fc fc fc fc fc fc
 ffff88003d56d580: 00 02 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================