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BUG: KASAN: use-after-free in put_pid_ns+0xf7/0x110 kernel/pid_namespace.c:202
Read of size 8 at addr ffff8880545a7de8 by task syz-executor.2/4005

CPU: 1 PID: 4005 Comm: syz-executor.2 Not tainted 4.14.184-syzkaller #0
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+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2b9 mm/kasan/report.c:393
 put_pid_ns+0xf7/0x110 kernel/pid_namespace.c:202
 free_nsproxy+0xf7/0x1f0 kernel/nsproxy.c:182
 switch_task_namespaces+0x8f/0xb0 kernel/nsproxy.c:229
 copy_process.part.0+0x3f47/0x6fa0 kernel/fork.c:1971
 copy_process kernel/fork.c:1586 [inline]
 _do_fork+0x180/0xc80 kernel/fork.c:2070
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c1d9
RSP: 002b:00007f0c51a93c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000001f00 RCX: 000000000045c1d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 339aa4b3a3f6a5a8
RBP: 00007f0c51a93ca0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000180 R11: 0000000000000246 R12: 000000000000005a
R13: 00007ffec9ebfaaf R14: 00007f0c51a949c0 R15: 000000000078bf0c

Allocated by task 4005:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc.part.0+0x4f/0xd0 mm/kasan/kasan.c:551
 kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
 kmem_cache_zalloc include/linux/slab.h:651 [inline]
 create_pid_namespace kernel/pid_namespace.c:116 [inline]
 copy_pid_ns+0x1b2/0xa70 kernel/pid_namespace.c:186
 create_new_namespaces+0x25f/0x730 kernel/nsproxy.c:94
 copy_namespaces+0x27b/0x310 kernel/nsproxy.c:165
 copy_process.part.0+0x2616/0x6fa0 kernel/fork.c:1774
 copy_process kernel/fork.c:1586 [inline]
 _do_fork+0x180/0xc80 kernel/fork.c:2070
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 4020:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xaf/0x190 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2699 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline]
 rcu_process_callbacks+0x78d/0x1180 kernel/rcu/tree.c:2946
 __do_softirq+0x254/0x9bf kernel/softirq.c:288

The buggy address belongs to the object at ffff8880545a75b0
 which belongs to the cache pid_namespace of size 2264
The buggy address is located 2104 bytes inside of
 2264-byte region [ffff8880545a75b0, ffff8880545a7e88)
The buggy address belongs to the page:
page:ffffea0001516980 count:1 mapcount:0 mapping:ffff8880545a6300 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff8880545a6300 0000000000000000 0000000100000003
raw: ffffea000099c4a0 ffff8880a655af48 ffff8880a6557cc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880545a7c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880545a7d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880545a7d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff8880545a7e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880545a7e80: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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