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BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:197 [inline]
BUG: KASAN: use-after-free in task_is_descendant.part.0+0x6a1/0x6f0 security/yama/yama_lsm.c:295
Read of size 8 at addr ffff888059820a20 by task syz-executor5/6105

CPU: 1 PID: 6105 Comm: syz-executor5 Not tainted 5.0.0-rc1-next-20190110 #9
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+0x1db/0x2d0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
 __read_once_size include/linux/compiler.h:197 [inline]
 task_is_descendant.part.0+0x6a1/0x6f0 security/yama/yama_lsm.c:295
 task_is_descendant security/yama/yama_lsm.c:282 [inline]
 yama_ptrace_access_check security/yama/yama_lsm.c:371 [inline]
 yama_ptrace_access_check+0x40d/0x10e8 security/yama/yama_lsm.c:358
 security_ptrace_access_check+0x71/0xb0 security/security.c:271
 __ptrace_may_access+0x555/0x930 kernel/ptrace.c:332
 ptrace_attach+0x200/0x660 kernel/ptrace.c:380
 __do_sys_ptrace kernel/ptrace.c:1140 [inline]
 __se_sys_ptrace kernel/ptrace.c:1120 [inline]
 __x64_sys_ptrace+0x25c/0x2c0 kernel/ptrace.c:1120
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457ec9
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9b49eb1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000065
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000457ec9
RDX: 0000000000000000 RSI: 0000000000000d17 RDI: 0000000000000010
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9b49eb26d4
R13: 00000000004c489e R14: 00000000004d7d98 R15: 00000000ffffffff

Allocated by task 8002:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc mm/kasan/common.c:496 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:469
 kasan_kmalloc mm/kasan/common.c:504 [inline]
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:411
 kmem_cache_alloc_node+0x144/0x710 mm/slab.c:3633
 alloc_task_struct_node kernel/fork.c:157 [inline]
 dup_task_struct kernel/fork.c:844 [inline]
 copy_process+0x4088/0x8740 kernel/fork.c:1753
 _do_fork+0x1a9/0x1170 kernel/fork.c:2227
 __do_sys_clone kernel/fork.c:2334 [inline]
 __se_sys_clone kernel/fork.c:2328 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2328
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 16:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:458
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:466
 __cache_free mm/slab.c:3487 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3749
 free_task_struct kernel/fork.c:162 [inline]
 free_task+0x170/0x1f0 kernel/fork.c:457
 __put_task_struct+0x2e0/0x630 kernel/fork.c:730
 put_task_struct include/linux/sched/task.h:98 [inline]
 delayed_put_task_struct+0x2fd/0x4d0 kernel/exit.c:181
 __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
 rcu_do_batch kernel/rcu/tree.c:2486 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2799 [inline]
 rcu_core+0xc4a/0x1680 kernel/rcu/tree.c:2780
 __do_softirq+0x30b/0xb11 kernel/softirq.c:292

The buggy address belongs to the object at ffff888059820540
 which belongs to the cache task_struct(97:syz5) of size 6080
The buggy address is located 1248 bytes inside of
 6080-byte region [ffff888059820540, ffff888059821d00)
The buggy address belongs to the page:
page:ffffea0001660800 count:1 mapcount:0 mapping:ffff8880a3764340 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea000244de88 ffffea0002529788 ffff8880a3764340
raw: 0000000000000000 ffff888059820540 0000000100000001 ffff888057ce47c0
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff888057ce47c0

Memory state around the buggy address:
 ffff888059820900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888059820980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888059820a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888059820a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888059820b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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