==================================================================
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 ffff888098c8e440 by task syz-executor.5/14135

CPU: 0 PID: 14135 Comm: syz-executor.5 Not tainted 5.2.0+ #70
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 20 f0 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 55 db 99 01 00 74 20 fb 66 0f 1f 44 00 00 <bf> 01 00 00 00 e8 92 98 15 fa 65 8b 05 a3 e8 c8 78 85 c0 74 06 41
RSP: 0018:ffff888051a6eff8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11a5e04 RBX: ffff8880a4362640 RCX: 0000000000000007
RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff8880a4362ecc
RBP: ffff888051a6f000 R08: 1ffffffff14a7750 R09: fffffbfff14a7751
R10: fffffbfff14a7750 R11: ffffffff8a53ba87 R12: ffff8880ae835540
R13: ffff888089c56580 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
 preempt_schedule_common+0x4f/0xe0 /kernel/sched/core.c:4025
 preempt_schedule+0x4b/0x60 /kernel/sched/core.c:4051
 ___preempt_schedule+0x16/0x18
 __kunmap_atomic /./include/linux/highmem.h:102 [inline]
 clear_highpage /./include/linux/highmem.h:215 [inline]
 kernel_init_free_pages /mm/page_alloc.c:1124 [inline]
 prep_new_page+0x231/0x330 /mm/page_alloc.c:2156
 get_page_from_freelist+0x31f7/0x39d0 /mm/page_alloc.c:3691
 __alloc_pages_nodemask+0x2d0/0x8f0 /mm/page_alloc.c:4725
 __alloc_pages /./include/linux/gfp.h:473 [inline]
 __alloc_pages_node /./include/linux/gfp.h:486 [inline]
 alloc_pages_vma+0x3c5/0x560 /mm/mempolicy.c:2088
 do_huge_pmd_wp_page+0xb73/0x2170 /mm/huge_memory.c:1351
 wp_huge_pmd /mm/memory.c:3741 [inline]
 __handle_mm_fault+0x14d2/0x3f20 /mm/memory.c:3954
 handle_mm_fault+0x1b5/0x6b0 /mm/memory.c:4001
 do_user_addr_fault /arch/x86/mm/fault.c:1444 [inline]
 __do_page_fault+0x536/0xdd0 /arch/x86/mm/fault.c:1510
 do_page_fault+0x71/0x5e1 /arch/x86/mm/fault.c:1541
 page_fault+0x1e/0x30 /arch/x86/entry/entry_64.S:1182
RIP: 0010:copy_user_enhanced_fast_string+0xe/0x20 /arch/x86/lib/copy_user_64.S:205
Code: 89 d1 c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 31 c0 0f 1f 00 c3 0f 1f 80 00 00 00 00 0f 1f 00 83 fa 40 0f 82 70 ff ff ff 89 d1 <f3> a4 31 c0 0f 1f 00 c3 66 2e 0f 1f 84 00 00 00 00 00 89 d1 f3 a4
RSP: 0018:ffff888051a6f9c8 EFLAGS: 00010206
RAX: 0000000000000001 RBX: 0000000000001000 RCX: 0000000000000fc3
RDX: 0000000000001000 RSI: ffff888082c0003d RDI: 0000000020a00000
RBP: ffff888051a6fa00 R08: ffffed1010580200 R09: 0000000000000000
R10: ffffed10105801ff R11: ffff888082c00fff R12: 00000000209fffc3
R13: ffff888082c00000 R14: 0000000020a00fc3 R15: 00007ffffffff000
 copy_page_to_iter_iovec /lib/iov_iter.c:211 [inline]
 copy_page_to_iter+0x36e/0xdb0 /lib/iov_iter.c:900
 process_vm_rw_pages /mm/process_vm_access.c:49 [inline]
 process_vm_rw_single_vec /mm/process_vm_access.c:120 [inline]
 process_vm_rw_core.isra.0+0x632/0xb10 /mm/process_vm_access.c:216
 process_vm_rw+0x21f/0x240 /mm/process_vm_access.c:284
 __do_sys_process_vm_readv /mm/process_vm_access.c:298 [inline]
 __se_sys_process_vm_readv /mm/process_vm_access.c:294 [inline]
 __x64_sys_process_vm_readv+0xe3/0x1a0 /mm/process_vm_access.c:294
 do_syscall_64+0xfd/0x6a0 /arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459819
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:00007fa3b1478c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000136
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000459819
RDX: 00000000000002a2 RSI: 0000000020000380 RDI: 0000000000000001
RBP: 000000000075bf20 R08: 00000000000001ce R09: 0000000000000000
R10: 0000000020002540 R11: 0000000000000246 R12: 00007fa3b14796d4
R13: 00000000004c69d9 R14: 00000000004db938 R15: 00000000ffffffff

Allocated by task 14135:
 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 14296:
 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_accept4 /net/socket.c:1789 [inline]
 __se_sys_accept4 /net/socket.c:1786 [inline]
 __x64_sys_accept4+0x97/0xf0 /net/socket.c:1786
 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 ffff888098c8e3c0
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 128 bytes inside of
 2048-byte region [ffff888098c8e3c0, ffff888098c8ebc0)
The buggy address belongs to the page:
page:ffffea0002632380 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0001a68b08 ffffea00027ea888 ffff8880aa400e00
raw: 0000000000000000 ffff888098c8e3c0 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888098c8e300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888098c8e380: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff888098c8e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff888098c8e480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888098c8e500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================