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BUG: KASAN: use-after-free in free_netdev+0x176/0x300 net/core/dev.c:9609
Read of size 8 at addr ffff8881ccc26538 by task syz-executor.1/5168

CPU: 0 PID: 5168 Comm: syz-executor.1 Not tainted 5.4.63-syzkaller-01128-g0ef1db7b69dd #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+0x1b0/0x21e lib/dump_stack.c:118
 print_address_description+0x96/0x5d0 mm/kasan/report.c:374
 __kasan_report+0x14b/0x1c0 mm/kasan/report.c:506
 kasan_report+0x27/0x50 mm/kasan/common.c:634
 free_netdev+0x176/0x300 net/core/dev.c:9609
 netdev_run_todo+0xbc4/0xe00 net/core/dev.c:9360
 rtnl_unlock net/core/rtnetlink.c:112 [inline]
 rtnetlink_rcv_msg+0x963/0xc20 net/core/rtnetlink.c:5256
 netlink_rcv_skb+0x1f0/0x460 net/netlink/af_netlink.c:2478
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x87c/0xa20 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x9a7/0xd40 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:638 [inline]
 sock_sendmsg net/socket.c:658 [inline]
 ____sys_sendmsg+0x56f/0x860 net/socket.c:2298
 ___sys_sendmsg net/socket.c:2352 [inline]
 __sys_sendmsg+0x26a/0x350 net/socket.c:2398
 do_syscall_64+0xcb/0x150 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d5b9
Code: 5d b4 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 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff2c31d7c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000002ce80 RCX: 000000000045d5b9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000007
RBP: 000000000118d020 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cfec
R13: 00007ffdb83e266f R14: 00007ff2c31d89c0 R15: 000000000118cfec

Allocated by task 5166:
 save_stack mm/kasan/common.c:69 [inline]
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc+0x117/0x1b0 mm/kasan/common.c:510
 __kmalloc+0xf7/0x2c0 mm/slub.c:3848
 kmalloc include/linux/slab.h:561 [inline]
 sk_prot_alloc+0xd6/0x290 net/core/sock.c:1605
 sk_alloc+0x33/0x340 net/core/sock.c:1659
 tun_chr_open+0x77/0x4a0 drivers/net/tun.c:3425
 misc_open+0x356/0x3d0 drivers/char/misc.c:141
 chrdev_open+0x60a/0x670 fs/char_dev.c:414
 do_dentry_open+0x8fa/0x1070 fs/open.c:809
 do_last fs/namei.c:3528 [inline]
 path_openat+0x1681/0x42d0 fs/namei.c:3646
 do_filp_open+0x1f7/0x430 fs/namei.c:3676
 do_sys_open+0x36f/0x7a0 fs/open.c:1106
 do_syscall_64+0xcb/0x150 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 5165:
 save_stack mm/kasan/common.c:69 [inline]
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x168/0x220 mm/kasan/common.c:471
 slab_free_hook mm/slub.c:1443 [inline]
 slab_free_freelist_hook+0xd0/0x150 mm/slub.c:1476
 slab_free mm/slub.c:3041 [inline]
 kfree+0x12b/0x5d0 mm/slub.c:4002
 sk_prot_free net/core/sock.c:1642 [inline]
 __sk_destruct+0x3f9/0x480 net/core/sock.c:1727
 tun_detach drivers/net/tun.c:740 [inline]
 tun_chr_close+0xb4/0xd0 drivers/net/tun.c:3461
 __fput+0x27d/0x6c0 fs/file_table.c:280
 task_work_run+0x176/0x1a0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:163 [inline]
 prepare_exit_to_usermode+0x286/0x2e0 arch/x86/entry/common.c:194
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8881ccc26000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1336 bytes inside of
 2048-byte region [ffff8881ccc26000, ffff8881ccc26800)
The buggy address belongs to the page:
page:ffffea0007330800 refcount:1 mapcount:0 mapping:ffff8881da80c000 index:0x0 compound_mapcount: 0
flags: 0x8000000000010200(slab|head)
raw: 8000000000010200 dead000000000100 dead000000000122 ffff8881da80c000
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881ccc26400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881ccc26480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881ccc26500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff8881ccc26580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881ccc26600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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