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BUG: KASAN: use-after-free in free_netdev+0x186/0x380 net/core/dev.c:9911
Read of size 8 at addr ffff8880a28cc6f8 by task syz-executor933/7277

CPU: 0 PID: 7277 Comm: syz-executor933 Not tainted 5.7.0-rc5-syzkaller #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+0x1e9/0x30e lib/dump_stack.c:118
 print_address_description+0x74/0x5c0 mm/kasan/report.c:382
 __kasan_report+0x103/0x1a0 mm/kasan/report.c:511
 kasan_report+0x4d/0x80 mm/kasan/common.c:625

Allocated by task 7274:
 save_stack mm/kasan/common.c:49 [inline]
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc+0x114/0x160 mm/kasan/common.c:495
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc+0x24b/0x330 mm/slab.c:3665
 kmalloc include/linux/slab.h:560 [inline]
 sk_prot_alloc+0xa7/0x2b0 net/core/sock.c:1604
 sk_alloc+0x35/0x990 net/core/sock.c:1658
 tun_chr_open+0x77/0x470 drivers/net/tun.c:3377
 misc_open+0x346/0x3c0 drivers/char/misc.c:141
 chrdev_open+0x498/0x580 fs/char_dev.c:414
 do_dentry_open+0x82e/0x10b0 fs/open.c:797
 do_open fs/namei.c:3229 [inline]
 path_openat+0x2790/0x38b0 fs/namei.c:3346
 do_filp_open+0x191/0x3a0 fs/namei.c:3373
 do_sys_openat2+0x463/0x770 fs/open.c:1148
 do_sys_open fs/open.c:1164 [inline]
 __do_sys_openat fs/open.c:1178 [inline]
 __se_sys_openat fs/open.c:1173 [inline]
 __x64_sys_openat+0x1c8/0x1f0 fs/open.c:1173
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 7275:
 save_stack mm/kasan/common.c:49 [inline]
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0x125/0x190 mm/kasan/common.c:456
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 sk_prot_free net/core/sock.c:1641 [inline]
 __sk_destruct+0x61d/0x740 net/core/sock.c:1725
 tun_detach drivers/net/tun.c:707 [inline]
 tun_chr_close+0x113/0x130 drivers/net/tun.c:3413
 __fput+0x2ed/0x750 fs/file_table.c:280
 task_work_run+0x147/0x1d0 kernel/task_work.c:123
 get_signal+0x1cae/0x1d60 kernel/signal.c:2533
 do_signal+0x33/0x610 arch/x86/kernel/signal.c:784
 exit_to_usermode_loop arch/x86/entry/common.c:161 [inline]
 prepare_exit_to_usermode+0x32a/0x600 arch/x86/entry/common.c:196
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff8880a28cc000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1784 bytes inside of
 4096-byte region [ffff8880a28cc000, ffff8880a28cd000)
The buggy address belongs to the page:
page:ffffea00028a3300 refcount:1 mapcount:0 mapping:000000000d52f25f index:0x0 head:ffffea00028a3300 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00028cd208 ffffea00022fb188 ffff8880aa402000
raw: 0000000000000000 ffff8880a28cc000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a28cc580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a28cc600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a28cc680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff8880a28cc700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a28cc780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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