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BUG: KASAN: use-after-free in x25_write_internal+0xde0/0xed0 net/x25/x25_subr.c:173
Read of size 4 at addr ffff88808f87399c by task syz-executor3/12089

CPU: 1 PID: 12089 Comm: syz-executor3 Not tainted 5.0.0-rc3+ #19
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+0x1db/0x2d0 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
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:134
 x25_write_internal+0xde0/0xed0 net/x25/x25_subr.c:173
 x25_release+0xd0/0x340 net/x25/af_x25.c:660
 __sock_release+0xd3/0x250 net/socket.c:579
 sock_close+0x1b/0x30 net/socket.c:1141
 __fput+0x3c5/0xb10 fs/file_table.c:278
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x1f4/0x2b0 kernel/task_work.c:113
 get_signal+0x168d/0x19b0 kernel/signal.c:2347
 do_signal+0x91/0x1ea0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2f7/0x3b0 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x696/0x800 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458099
Code: 6d 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 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0295929c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: fffffffffffffe00 RBX: 0000000000000003 RCX: 0000000000458099
RDX: 0000000000000012 RSI: 0000000020000200 RDI: 0000000000000005
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f029592a6d4
R13: 00000000004be5fe R14: 00000000004cece0 R15: 00000000ffffffff

Allocated by task 14840:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc mm/kasan/common.c:496 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:469
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:504
 kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3609
 kmalloc include/linux/slab.h:545 [inline]
 x25_link_device_up+0xa5/0x4f0 net/x25/x25_link.c:249
 x25_device_event+0x116/0x2b0 net/x25/af_x25.c:242
 notifier_call_chain+0x179/0x380 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+0x173/0x470 net/core/dev.c:7605
 dev_change_flags+0x10d/0x170 net/core/dev.c:7643
 dev_ifsioc+0x359/0xa50 net/core/dev_ioctl.c:237
 dev_ioctl+0x1b8/0xc70 net/core/dev_ioctl.c:488
 sock_do_ioctl+0x1d9/0x400 net/socket.c:973
 sock_ioctl+0x32f/0x6c0 net/socket.c:1074
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x107b/0x17d0 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+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 12089:
 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:458
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:466
 __cache_free mm/slab.c:3487 [inline]
 kfree+0xcf/0x230 mm/slab.c:3806
 x25_neigh_put include/net/x25.h:253 [inline]
 x25_connect+0xa58/0x1050 net/x25/af_x25.c:823
 __sys_connect+0x357/0x490 net/socket.c:1664
 __do_sys_connect net/socket.c:1675 [inline]
 __se_sys_connect net/socket.c:1672 [inline]
 __x64_sys_connect+0x73/0xb0 net/socket.c:1672
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808f873980
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 28 bytes inside of
 256-byte region [ffff88808f873980, ffff88808f873a80)
The buggy address belongs to the page:
page:ffffea00023e1cc0 count:1 mapcount:0 mapping:ffff88812c3f07c0 index:0xffff88808f873200
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002325c48 ffffea00021a2208 ffff88812c3f07c0
raw: ffff88808f873200 ffff88808f8730c0 0000000100000009 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808f873880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808f873900: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff88808f873980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88808f873a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808f873a80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
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