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BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
BUG: KASAN: use-after-free in refcount_sub_and_test_checked+0x80/0x1f0 lib/refcount.c:179
Read of size 4 at addr ffff8880858887c8 by task syz-executor.2/4365

CPU: 0 PID: 4365 Comm: syz-executor.2 Not tainted 5.0.0-rc7+ #91
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.cold+0x7c/0x20d mm/kasan/report.c:187
 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 kasan_check_read+0x11/0x20 mm/kasan/common.c:100
 atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
 refcount_sub_and_test_checked+0x80/0x1f0 lib/refcount.c:179
 refcount_dec_and_test_checked+0x1b/0x20 lib/refcount.c:212
 x25_neigh_put include/net/x25.h:252 [inline]
 x25_connect+0x8bc/0xde0 net/x25/af_x25.c:824
 __sys_connect+0x266/0x330 net/socket.c:1684
 __do_sys_connect net/socket.c:1695 [inline]
 __se_sys_connect net/socket.c:1692 [inline]
 __x64_sys_connect+0x73/0xb0 net/socket.c:1692
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457e29
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0202148c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457e29
RDX: 0000000000000012 RSI: 0000000020000000 RDI: 0000000000000005
RBP: 000000000073c0e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f02021496d4
R13: 00000000004be362 R14: 00000000004ceb98 R15: 00000000ffffffff

Allocated by task 22764:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc mm/kasan/common.c:495 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:468
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:509
 kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3615
 kmalloc include/linux/slab.h:545 [inline]
 x25_link_device_up+0x46/0x3f0 net/x25/x25_link.c:249
 x25_device_event+0x116/0x2b0 net/x25/af_x25.c:242
 notifier_call_chain+0xc7/0x240 kernel/notifier.c:93
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x2e/0x40 kernel/notifier.c:401
 call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1739
 call_netdevice_notifiers_extack net/core/dev.c:1751 [inline]
 call_netdevice_notifiers net/core/dev.c:1765 [inline]
 __dev_notify_flags+0x121/0x2c0 net/core/dev.c:7605
 dev_change_flags+0x10d/0x170 net/core/dev.c:7643
 dev_ifsioc+0x2b0/0x940 net/core/dev_ioctl.c:237
 dev_ioctl+0x1b8/0xc70 net/core/dev_ioctl.c:488
 sock_do_ioctl+0x1bd/0x300 net/socket.c:994
 sock_ioctl+0x32b/0x610 net/socket.c:1095
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xd6e/0x1390 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4348:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:457
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:465
 __cache_free mm/slab.c:3494 [inline]
 kfree+0xcf/0x230 mm/slab.c:3811
 x25_neigh_put include/net/x25.h:253 [inline]
 x25_connect+0x8d8/0xde0 net/x25/af_x25.c:824
 __sys_connect+0x266/0x330 net/socket.c:1684
 __do_sys_connect net/socket.c:1695 [inline]
 __se_sys_connect net/socket.c:1692 [inline]
 __x64_sys_connect+0x73/0xb0 net/socket.c:1692
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888085888700
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 200 bytes inside of
 256-byte region [ffff888085888700, ffff888085888800)
The buggy address belongs to the page:
page:ffffea0002162200 count:1 mapcount:0 mapping:ffff88812c3f07c0 index:0xffff888085888200
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002796b88 ffffea00018b0408 ffff88812c3f07c0
raw: ffff888085888200 ffff8880858880c0 000000010000000b 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888085888680: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888085888700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888085888780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888085888800: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
 ffff888085888880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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netlink: 'syz-executor.0': attribute type 12 has an invalid length.