==================================================================
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: use-after-free in refcount_inc_not_zero_checked+0x81/0x200 lib/refcount.c:123
Read of size 4 at addr ffff8880701ee680 by task syz-executor.5/17112

CPU: 0 PID: 17112 Comm: syz-executor.5 Not tainted 5.3.0-rc1+ #77
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
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
 __kasan_check_read+0x11/0x20 mm/kasan/common.c:92
 atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
 refcount_inc_not_zero_checked+0x81/0x200 lib/refcount.c:123
 refcount_inc_checked+0x17/0x70 lib/refcount.c:156
 sock_hold include/net/sock.h:649 [inline]
 sk_add_node include/net/sock.h:701 [inline]
 nr_insert_socket+0x2d/0xe0 net/netrom/af_netrom.c:137
 nr_rx_frame+0x1605/0x1e73 net/netrom/af_netrom.c:1023
 nr_loopback_timer+0x7b/0x170 net/netrom/nr_loopback.c:59
 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:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x54/0x90 kernel/locking/spinlock.c:199
Code: c0 a0 f1 d2 88 48 ba 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 75 33 48 83 3d c5 04 95 01 00 74 20 fb 66 0f 1f 44 00 00 <bf> 01 00 00 00 e8 32 e2 10 fa 65 8b 05 93 10 c4 78 85 c0 74 06 41
RSP: 0018:ffff888070727408 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11a5e34 RBX: ffff8880602d6080 RCX: 1ffffffff134b2b6
RDX: dffffc0000000000 RSI: ffffffff8178256e RDI: ffffffff873decb8
RBP: ffff888070727410 R08: ffff8880602d6080 R09: ffffed1015d06ab1
R10: ffffed1015d06ab0 R11: ffff8880ae835583 R12: ffff8880ae835580
R13: ffff888099e9e700 R14: 0000000000000000 R15: 0000000000000001
 finish_lock_switch kernel/sched/core.c:3004 [inline]
 finish_task_switch+0x147/0x720 kernel/sched/core.c:3104
 context_switch kernel/sched/core.c:3257 [inline]
 __schedule+0x75d/0x1580 kernel/sched/core.c:3880
 schedule+0xa8/0x270 kernel/sched/core.c:3944
 schedule_hrtimeout_range_clock+0x1b1/0x380 kernel/time/hrtimer.c:1938
 schedule_hrtimeout_range+0x2b/0x40 kernel/time/hrtimer.c:1983
 poll_schedule_timeout.constprop.0+0x11a/0x200 fs/select.c:243
 do_select+0x1225/0x16f0 fs/select.c:603
 core_sys_select+0x564/0x890 fs/select.c:677
 do_pselect fs/select.c:759 [inline]
 __do_sys_pselect6 fs/select.c:784 [inline]
 __se_sys_pselect6 fs/select.c:769 [inline]
 __x64_sys_pselect6+0x3df/0x490 fs/select.c:769
 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: fd 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fceba967c78 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040
RBP: 000000000075bfc8 R08: 0000000020000200 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 00007fceba9686d4
R13: 00000000004c69fc R14: 00000000004db968 R15: 00000000ffffffff

Allocated by task 17112:
 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_kmalloc+0x9/0x10 mm/kasan/common.c:501
 __do_kmalloc mm/slab.c:3655 [inline]
 __kmalloc+0x163/0x770 mm/slab.c:3664
 kmalloc include/linux/slab.h:557 [inline]
 sk_prot_alloc+0x23a/0x310 net/core/sock.c:1603
 sk_alloc+0x39/0xf70 net/core/sock.c:1657
 nr_make_new net/netrom/af_netrom.c:476 [inline]
 nr_rx_frame+0x733/0x1e73 net/netrom/af_netrom.c:959
 nr_loopback_timer+0x7b/0x170 net/netrom/nr_loopback.c:59
 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

Freed by task 17521:
 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]
 kfree+0x10a/0x2c0 mm/slab.c:3756
 sk_prot_free net/core/sock.c:1640 [inline]
 __sk_destruct+0x4f7/0x6e0 net/core/sock.c:1726
 sk_destruct+0x86/0xa0 net/core/sock.c:1734
 __sk_free+0xfb/0x360 net/core/sock.c:1745
 sk_free+0x42/0x50 net/core/sock.c:1756
 sock_put include/net/sock.h:1725 [inline]
 sock_efree+0x61/0x80 net/core/sock.c:2042
 skb_release_head_state+0xeb/0x250 net/core/skbuff.c:652
 skb_release_all+0x16/0x60 net/core/skbuff.c:663
 __kfree_skb net/core/skbuff.c:679 [inline]
 kfree_skb net/core/skbuff.c:697 [inline]
 kfree_skb+0x101/0x3c0 net/core/skbuff.c:691
 nr_accept+0x56e/0x700 net/netrom/af_netrom.c:819
 __sys_accept4+0x34e/0x6a0 net/socket.c:1754
 __do_sys_accept net/socket.c:1795 [inline]
 __se_sys_accept net/socket.c:1792 [inline]
 __x64_sys_accept+0x75/0xb0 net/socket.c:1792
 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880701ee600
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 128 bytes inside of
 2048-byte region [ffff8880701ee600, ffff8880701eee00)
The buggy address belongs to the page:
page:ffffea0001c07b80 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0001c05288 ffffea000286ba08 ffff8880aa400e00
raw: 0000000000000000 ffff8880701ee600 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880701ee580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880701ee600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880701ee680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880701ee700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880701ee780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================