==================================================================
BUG: KASAN: use-after-free in p9_conn_cancel+0x400/0x4c0 net/9p/trans_fd.c:218
9pnet: Insufficient options for proto=fd
Read of size 8 at addr ffff880198c3c098 by task kworker/0:3/1838

CPU: 0 PID: 1838 Comm: kworker/0:3 Not tainted 4.9.120-gf85543b #24
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events p9_poll_workfn
 ffff8801ceabfaa0 ffffffff81eb8049 ffffea0006630f00 ffff880198c3c098
 0000000000000000 ffff880198c3c098 dffffc0000000000 ffff8801ceabfad8
 ffffffff8156ab7f ffff880198c3c098 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81eb8049>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb8049>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8156ab7f>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff8156af89>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff8156af89>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153e7f4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff839c8b90>] p9_conn_cancel+0x400/0x4c0 net/9p/trans_fd.c:218
 [<ffffffff839c91a2>] p9_poll_mux net/9p/trans_fd.c:630 [inline]
 [<ffffffff839c91a2>] p9_poll_workfn+0x222/0x330 net/9p/trans_fd.c:1097
 [<ffffffff8118eea1>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118fc96>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ee0d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839ffe9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

The buggy address belongs to the page:
page:ffffea0006630f00 count:0 mapcount:-127 mapping:          (null) index:0x0
flags: 0x8000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff880198c3bf80: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 ffff880198c3c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff880198c3c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff880198c3c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff880198c3c180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
FAT-fs (loop4): bogus number of reserved sectors
FAT-fs (loop4): Can't find a valid FAT filesystem