==================================================================
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 ffff88804f636680 by task syz-executor.1/31320

CPU: 0 PID: 31320 Comm: syz-executor.1 Not tainted 5.2.0+ #71
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+0x16f/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/0x700 /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+0x66c/0x16a0 /kernel/time/timer.c:1698
 __do_softirq+0x30d/0x970 /kernel/softirq.c:292
 invoke_softirq /kernel/softirq.c:373 [inline]
 irq_exit+0x1d0/0x200 /kernel/softirq.c:413
 exiting_irq /./arch/x86/include/asm/apic.h:537 [inline]
 smp_apic_timer_interrupt+0x14e/0x550 /arch/x86/kernel/apic/apic.c:1095
 apic_timer_interrupt+0xf/0x20 /arch/x86/entry/entry_64.S:828
 </IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x3b/0x50 /kernel/kcov.c:107
Code: a6 90 7e 81 e2 00 01 1f 00 48 8b 75 08 75 2b 8b 90 a8 12 00 00 83 fa 02 75 20 48 8b 88 b0 12 00 00 8b 80 ac 12 00 00 48 8b 11 <48> 83 c2 01 48 39 d0 76 07 48 89 34 d1 48 89 11 5d c3 0f 1f 00 65
RSP: 0018:ffff88803c4c6e38 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc90008353000
RDX: 000000000000d03a RSI: ffffffff81626543 RDI: 0000000000000005
RBP: ffff88803c4c6e38 R08: ffff88805bf32640 R09: ffffed1014489828
R10: ffffed1014489827 R11: ffff8880a244c13f R12: fffffbfff11a5c71
R13: dffffc0000000000 R14: 1ffffffff11a5c73 R15: ffff8880a2488800
 arch_local_save_flags /./arch/x86/include/asm/paravirt.h:763 [inline]
 arch_local_irq_save /./arch/x86/include/asm/paravirt.h:785 [inline]
 seqcount_lockdep_reader_access /./include/linux/seqlock.h:80 [inline]
 read_seqcount_begin /./include/linux/seqlock.h:164 [inline]
 ktime_get+0x73/0x2f0 /kernel/time/timekeeping.c:752
 ktime_get_ns /./include/linux/timekeeping.h:154 [inline]
 blk_mq_rq_ctx_init /block/blk-mq.c:329 [inline]
 blk_mq_get_request+0x9d9/0x1590 /block/blk-mq.c:396
 blk_mq_make_request+0x418/0x20d0 /block/blk-mq.c:1960
 generic_make_request /block/blk-core.c:1052 [inline]
 generic_make_request+0x23c/0xb10 /block/blk-core.c:994
 submit_bio+0x104/0x4d0 /block/blk-core.c:1163
 submit_bh_wbc+0x6b6/0x900 /fs/buffer.c:3095
 submit_bh /fs/buffer.c:3101 [inline]
 __sync_dirty_buffer+0x12b/0x350 /fs/buffer.c:3187
 sync_dirty_buffer+0x1b/0x20 /fs/buffer.c:3200
 ext4_write_inode+0x54b/0x600 /fs/ext4/inode.c:5455
 write_inode /fs/fs-writeback.c:1224 [inline]
 __writeback_single_inode+0xcac/0x1280 /fs/fs-writeback.c:1423
 writeback_single_inode+0x2cc/0x430 /fs/fs-writeback.c:1477
 sync_inode /fs/fs-writeback.c:2514 [inline]
 sync_inode_metadata+0xa8/0xe0 /fs/fs-writeback.c:2534
 __generic_file_fsync+0x169/0x200 /fs/libfs.c:1007
 ext4_sync_file+0x81c/0x1540 /fs/ext4/fsync.c:120
 vfs_fsync_range+0x141/0x230 /fs/sync.c:197
 generic_write_sync /./include/linux/fs.h:2793 [inline]
 ext4_file_write_iter+0x839/0x1430 /fs/ext4/file.c:281
 call_write_iter /./include/linux/fs.h:1870 [inline]
 do_iter_readv_writev+0x5f8/0x8f0 /fs/read_write.c:693
 do_iter_write /fs/read_write.c:970 [inline]
 do_iter_write+0x184/0x610 /fs/read_write.c:951
 vfs_iter_write+0x77/0xb0 /fs/read_write.c:983
 iter_file_splice_write+0x66d/0xbe0 /fs/splice.c:746
 do_splice_from /fs/splice.c:848 [inline]
 direct_splice_actor+0x123/0x190 /fs/splice.c:1020
 splice_direct_to_actor+0x366/0x970 /fs/splice.c:975
 do_splice_direct+0x1da/0x2a0 /fs/splice.c:1063
 do_sendfile+0x597/0xd00 /fs/read_write.c:1464
 __do_sys_sendfile64 /fs/read_write.c:1519 [inline]
 __se_sys_sendfile64 /fs/read_write.c:1511 [inline]
 __x64_sys_sendfile64+0x15a/0x220 /fs/read_write.c:1511
 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:00007f61830cdc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459829
RDX: 0000000020000000 RSI: 0000000000000006 RDI: 0000000000000006
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 00008080fffffffe R11: 0000000000000246 R12: 00007f61830ce6d4
R13: 00000000004c6e87 R14: 00000000004dc238 R15: 00000000ffffffff

Allocated by task 31320:
 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+0x163/0x760 /mm/slab.c:3664
 kmalloc /./include/linux/slab.h:557 [inline]
 sk_prot_alloc+0x23a/0x310 /net/core/sock.c:1603
 sk_alloc+0x39/0xf60 /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/0x700 /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+0x66c/0x16a0 /kernel/time/timer.c:1698
 __do_softirq+0x30d/0x970 /kernel/softirq.c:292

Freed by task 31321:
 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/0x2a0 /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+0x101/0x380 /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 ffff88804f636600
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 128 bytes inside of
 2048-byte region [ffff88804f636600, ffff88804f636e00)
The buggy address belongs to the page:
page:ffffea00013d8d80 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea00022fdd88 ffff8880aa401948 ffff8880aa400e00
raw: 0000000000000000 ffff88804f636600 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88804f636580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88804f636600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88804f636680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88804f636700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804f636780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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