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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 ffff8880a7562080 by task syz-executor.4/9508

CPU: 1 PID: 9508 Comm: syz-executor.4 Not tainted 5.3.0-next-20190930 #0
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+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:634
 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]
 nr_release+0x62/0x3e0 net/netrom/af_netrom.c:520
 __sock_release+0xce/0x280 net/socket.c:591
 sock_close+0x1e/0x30 net/socket.c:1269
 __fput+0x2ff/0x890 fs/file_table.c:280
 ____fput+0x16/0x20 fs/file_table.c:313
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x413711
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffeebc6e6d0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000413711
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 0000000000000001 R08: ffffffffffffffff R09: ffffffffffffffff
R10: 00007ffeebc6e7b0 R11: 0000000000000293 R12: 000000000075c9a0
R13: 000000000075c9a0 R14: 0000000000760c38 R15: 000000000075c124

Allocated by task 9509:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:510 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
 __do_kmalloc mm/slab.c:3655 [inline]
 __kmalloc+0x163/0x770 mm/slab.c:3664
 kmalloc include/linux/slab.h:561 [inline]
 sk_prot_alloc+0x23a/0x310 net/core/sock.c:1603
 sk_alloc+0x39/0xf70 net/core/sock.c:1657
 nr_create+0xb9/0x5e0 net/netrom/af_netrom.c:433
 __sock_create+0x3d8/0x730 net/socket.c:1419
 sock_create net/socket.c:1470 [inline]
 __sys_socket+0x103/0x220 net/socket.c:1512
 __do_sys_socket net/socket.c:1521 [inline]
 __se_sys_socket net/socket.c:1519 [inline]
 __x64_sys_socket+0x73/0xb0 net/socket.c:1519
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9508:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
 __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]
 nr_release+0x356/0x3e0 net/netrom/af_netrom.c:554
 __sock_release+0xce/0x280 net/socket.c:591
 sock_close+0x1e/0x30 net/socket.c:1269
 __fput+0x2ff/0x890 fs/file_table.c:280
 ____fput+0x16/0x20 fs/file_table.c:313
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a7562000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 128 bytes inside of
 2048-byte region [ffff8880a7562000, ffff8880a7562800)
The buggy address belongs to the page:
page:ffffea00029d5880 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea00024da548 ffffea00025cec08 ffff8880aa400e00
raw: 0000000000000000 ffff8880a7562000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a7561f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a7562000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a7562080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880a7562100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a7562180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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