WARNING in dma_buf_vunmap

[syzbot]

syzbot has bisected this bug to:

commit d5e73f7be850323ae3adbbe84ed37a38b0c31476
Author: Mahesh Bandewar <maheshb at google.com>
Date:   Wed Mar 8 18:55:51 2017 +0000

     bonding: restructure arp-monitor

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15e679f7200000
start commit:   d5e73f7b bonding: restructure arp-monitor
git tree:       upstream
final crash:    https://syzkaller.appspot.com/x/report.txt?x=17e679f7200000
console output: https://syzkaller.appspot.com/x/log.txt?x=13e679f7200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4a0a89f12ca9b0f5
dashboard link: https://syzkaller.appspot.com/bug?extid=a9317fe7ad261fc76b88
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16f7b6f5400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=105a2783400000

Reported-by: syzbot+a9317fe7ad261fc76b88 at syzkaller.appspotmail.com
Fixes: d5e73f7b ("bonding: restructure arp-monitor")