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BUG: KASAN: use-after-free in alloc_pid+0x9a6/0xa00 kernel/pid.c:236
Read of size 4 at addr ffff8801cff8a418 by task syz-executor7/29125

CPU: 1 PID: 29125 Comm: syz-executor7 Not tainted 4.16.0-rc7+ #7
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+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 alloc_pid+0x9a6/0xa00 kernel/pid.c:236
 copy_process.part.38+0x2516/0x4bd0 kernel/fork.c:1807
 copy_process kernel/fork.c:1606 [inline]
 _do_fork+0x1f7/0xf70 kernel/fork.c:2087
 SYSC_clone kernel/fork.c:2194 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2188
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x454e79
RSP: 002b:00007ff62b096c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ff62b0976d4 RCX: 0000000000454e79
RDX: 00000000209c4ffc RSI: 0000000020e69000 RDI: 0000000030000100
RBP: 000000000072bea0 R08: 0000000020a46000 R09: 0000000000000000
R10: 00000000201cc000 R11: 0000000000000246 R12: 0000000000000014
R13: 0000000000000051 R14: 00000000006f2838 R15: 000000000000002d

Allocated by task 29125:
 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:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3542
 kmem_cache_zalloc include/linux/slab.h:691 [inline]
 create_pid_namespace kernel/pid_namespace.c:116 [inline]
 copy_pid_ns+0x257/0xc60 kernel/pid_namespace.c:175
 create_new_namespaces+0x307/0x880 kernel/nsproxy.c:94
 copy_namespaces+0x340/0x400 kernel/nsproxy.c:165
 copy_process.part.38+0x2380/0x4bd0 kernel/fork.c:1796
 copy_process kernel/fork.c:1606 [inline]
 _do_fork+0x1f7/0xf70 kernel/fork.c:2087
 SYSC_clone kernel/fork.c:2194 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2188
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4493:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3486 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3744
 delayed_free_pidns+0x82/0xb0 kernel/pid_namespace.c:157
 __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
 rcu_do_batch kernel/rcu/tree.c:2674 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2933 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2900 [inline]
 rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2917
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801cff8a3d0
 which belongs to the cache pid_namespace of size 240
The buggy address is located 72 bytes inside of
 240-byte region [ffff8801cff8a3d0, ffff8801cff8a4c0)
The buggy address belongs to the page:
page:ffffea00073fe280 count:1 mapcount:0 mapping:ffff8801cff8a040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cff8a040 0000000000000000 000000010000000d
raw: ffffea00070ba0e0 ffff8801d4036748 ffff8801d4eec080 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cff8a300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cff8a380: fb fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb
>ffff8801cff8a400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8801cff8a480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8801cff8a500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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