TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
==================================================================
BUG: KASAN: use-after-free in tcp_probe_timer net/ipv4/tcp_timer.c:360 [inline]
BUG: KASAN: use-after-free in tcp_write_timer_handler+0x8c6/0x8d0 net/ipv4/tcp_timer.c:596
Read of size 4 at addr ffff888087e1c690 by task syz-executor.5/30252

CPU: 1 PID: 30252 Comm: syz-executor.5 Not tainted 5.2.0+ #67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
 __kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
 kasan_report+0x12/0x17 mm/kasan/common.c:612
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:131
 tcp_probe_timer net/ipv4/tcp_timer.c:360 [inline]
 tcp_write_timer_handler+0x8c6/0x8d0 net/ipv4/tcp_timer.c:596
 tcp_write_timer+0xa8/0x1e0 net/ipv4/tcp_timer.c:612
 call_timer_fn+0x1ac/0x780 kernel/time/timer.c:1322
 expire_timers kernel/time/timer.c:1366 [inline]
 __run_timers kernel/time/timer.c:1685 [inline]
 __run_timers kernel/time/timer.c:1653 [inline]
 run_timer_softirq+0x697/0x17a0 kernel/time/timer.c:1698
 __do_softirq+0x262/0x98c kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x19b/0x1e0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:537 [inline]
 smp_apic_timer_interrupt+0x1a3/0x610 arch/x86/kernel/apic/apic.c:1095
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:828
 </IRQ>
RIP: 0010:__find_get_block+0x289/0xdb0 fs/buffer.c:1294
Code: ff df 48 c1 ea 03 80 3c 02 00 0f 85 1c 0a 00 00 48 83 3d 49 f8 0d 07 00 0f 84 41 08 00 00 e8 fe 8c ad ff fb 66 0f 1f 44 00 00 <4d> 85 ff 0f 84 f1 01 00 00 e8 e9 8c ad ff 0f 1f 44 00 00 e8 df 8c
RSP: 0018:ffff8880674bf970 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13
RAX: ffff888061898100 RBX: ffff8880926a43f0 RCX: 0000000000000007
RDX: 0000000000000000 RSI: ffffffff81c4f7e2 RDI: ffff88806189898c
RBP: ffff8880674bf9d0 R08: 1ffffffff14a7753 R09: fffffbfff14a7754
R10: fffffbfff14a7753 R11: ffffffff8a53ba9f R12: 0000000000000000
R13: 0000000000000014 R14: 0000000000031840 R15: ffff8880926a43f0
 __getblk_gfp+0x38/0xa10 fs/buffer.c:1318
 sb_getblk include/linux/buffer_head.h:325 [inline]
 ext4_read_inode_bitmap+0x2b5/0x1a50 fs/ext4/ialloc.c:139
 ext4_free_inode+0x5fe/0x1490 fs/ext4/ialloc.c:288
 ext4_evict_inode+0xe7d/0x14e0 fs/ext4/inode.c:333
 evict+0x306/0x680 fs/inode.c:571
 iput_final fs/inode.c:1560 [inline]
 iput+0x530/0x8b0 fs/inode.c:1586
 do_unlinkat+0x44c/0x6d0 fs/namei.c:4069
 __do_sys_unlink fs/namei.c:4110 [inline]
 __se_sys_unlink fs/namei.c:4108 [inline]
 __x64_sys_unlink+0x42/0x50 fs/namei.c:4108
 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459577
Code: 00 66 90 b8 58 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 57 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 7d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffce8965878 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000459577
RDX: 00007ffce8965890 RSI: 00007ffce8965890 RDI: 00007ffce8965920
RBP: 0000000000001a5a R08: 0000000000000000 R09: 000000000000000d
R10: 0000000000000006 R11: 0000000000000246 R12: 00007ffce89669b0
R13: 0000555556dcd940 R14: 0000000000000000 R15: 00007ffce89669b0

Allocated by task 9415:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:487 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:460
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:495
 slab_post_alloc_hook mm/slab.h:520 [inline]
 slab_alloc mm/slab.c:3319 [inline]
 kmem_cache_alloc+0x121/0x710 mm/slab.c:3483
 kmem_cache_zalloc include/linux/slab.h:738 [inline]
 net_alloc net/core/net_namespace.c:410 [inline]
 copy_net_ns+0xf1/0x41f net/core/net_namespace.c:462
 create_new_namespaces+0x400/0x7b0 kernel/nsproxy.c:103
 unshare_nsproxy_namespaces+0xc2/0x200 kernel/nsproxy.c:202
 ksys_unshare+0x444/0x980 kernel/fork.c:2831
 __do_sys_unshare kernel/fork.c:2899 [inline]
 __se_sys_unshare kernel/fork.c:2897 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:2897
 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9747:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:449
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:457
 __cache_free mm/slab.c:3425 [inline]
 kmem_cache_free+0x86/0x320 mm/slab.c:3693
 net_free net/core/net_namespace.c:438 [inline]
 net_drop_ns.part.0+0x70/0x90 net/core/net_namespace.c:445
 net_drop_ns net/core/net_namespace.c:444 [inline]
 cleanup_net+0x77a/0xa70 net/core/net_namespace.c:613
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff888087e1c0c0
 which belongs to the cache net_namespace of size 6784
The buggy address is located 1488 bytes inside of
 6784-byte region [ffff888087e1c0c0, ffff888087e1db40)
The buggy address belongs to the page:
page:ffffea00021f8700 refcount:1 mapcount:0 mapping:ffff88821b69e1c0 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffff8880a9983448 ffffea000264ff08 ffff88821b69e1c0
raw: 0000000000000000 ffff888087e1c0c0 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888087e1c580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888087e1c600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888087e1c680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888087e1c700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888087e1c780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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