[Bridge] [syzbot] [net?] unregister_netdevice: waiting for DEV to become free (8)

[syzbot <syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    67faabbde36b selftests/bpf: Add missing prototypes for sev..
git tree:       bpf-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1381363b280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5335204dcdecfda
dashboard link: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=132faf93280000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10532add280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/751a0490d875/disk-67faabbd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2c5106cd9f1f/vmlinux-67faabbd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/62c1154294e4/bzImage-67faabbd.xz

The issue was bisected to:

commit ad2f99aedf8fa77f3ae647153284fa63c43d3055
Author: Arnd Bergmann <arnd@arndb.de>
Date:   Tue Jul 27 13:45:16 2021 +0000

    net: bridge: move bridge ioctls out of .ndo_do_ioctl

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=146de6f1280000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=166de6f1280000
console output: https://syzkaller.appspot.com/x/log.txt?x=126de6f1280000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com
Fixes: ad2f99aedf8f ("net: bridge: move bridge ioctls out of .ndo_do_ioctl")

unregister_netdevice: waiting for bridge0 to become free. Usage count = 2
leaked reference.
 __netdev_tracker_alloc include/linux/netdevice.h:4070 [inline]
 netdev_hold include/linux/netdevice.h:4099 [inline]
 dev_ifsioc+0xbc0/0xeb0 net/core/dev_ioctl.c:408
 dev_ioctl+0x250/0x1090 net/core/dev_ioctl.c:605
 sock_do_ioctl+0x15a/0x230 net/socket.c:1215
 sock_ioctl+0x1f8/0x680 net/socket.c:1318
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

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If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup