KASAN: use-after-free Read in __queue_work (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: ca04b3cca11a Merge tag 'armsoc-fixes' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1066e6dc400000
kernel config: https://syzkaller.appspot.com/x/.config?x=2ca6c7a31d407f86
dashboard link: https://syzkaller.appspot.com/bug?extid=1c9db6a163a4000d0765
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1473a452400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14087748400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1c9db6...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in constant_test_bit
arch/x86/include/asm/bitops.h:328 [inline]
BUG: KASAN: use-after-free in work_is_static_object+0x39/0x40
kernel/workqueue.c:442
Read of size 8 at addr ffff8801d7a7fda0 by task kworker/0:2/27

CPU: 0 PID: 27 Comm: kworker/0:2 Not tainted 4.18.0-rc3+ #137
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events p9_poll_workfn
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
constant_test_bit arch/x86/include/asm/bitops.h:328 [inline]
work_is_static_object+0x39/0x40 kernel/workqueue.c:442
debug_object_activate+0x2fc/0x690 lib/debugobjects.c:508
debug_work_activate kernel/workqueue.c:491 [inline]
__queue_work+0x1ca/0x1410 kernel/workqueue.c:1380
queue_work_on+0x19a/0x1e0 kernel/workqueue.c:1486
queue_work include/linux/workqueue.h:512 [inline]
schedule_work include/linux/workqueue.h:570 [inline]
p9_poll_mux net/9p/trans_fd.c:628 [inline]
p9_poll_workfn+0x55e/0x6d0 net/9p/trans_fd.c:1107
process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
kthread+0x345/0x410 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Allocated by task 4537:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
kmalloc include/linux/slab.h:513 [inline]
kzalloc include/linux/slab.h:707 [inline]
p9_fd_open net/9p/trans_fd.c:796 [inline]
p9_fd_create+0x1a7/0x3f0 net/9p/trans_fd.c:1036
p9_client_create+0x915/0x16c9 net/9p/client.c:1062
v9fs_session_init+0x21a/0x1a80 fs/9p/v9fs.c:400
v9fs_mount+0x7c/0x900 fs/9p/vfs_super.c:135
mount_fs+0xae/0x328 fs/super.c:1277
vfs_kern_mount.part.34+0xdc/0x4e0 fs/namespace.c:1037
vfs_kern_mount fs/namespace.c:1027 [inline]
do_new_mount fs/namespace.c:2518 [inline]
do_mount+0x581/0x30e0 fs/namespace.c:2848
ksys_mount+0x12d/0x140 fs/namespace.c:3064
__do_sys_mount fs/namespace.c:3078 [inline]
__se_sys_mount fs/namespace.c:3075 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4537:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xd9/0x260 mm/slab.c:3813
p9_fd_close+0x416/0x5b0 net/9p/trans_fd.c:893
p9_client_create+0xac2/0x16c9 net/9p/client.c:1076
v9fs_session_init+0x21a/0x1a80 fs/9p/v9fs.c:400
v9fs_mount+0x7c/0x900 fs/9p/vfs_super.c:135
mount_fs+0xae/0x328 fs/super.c:1277
vfs_kern_mount.part.34+0xdc/0x4e0 fs/namespace.c:1037
vfs_kern_mount fs/namespace.c:1027 [inline]
do_new_mount fs/namespace.c:2518 [inline]
do_mount+0x581/0x30e0 fs/namespace.c:2848
ksys_mount+0x12d/0x140 fs/namespace.c:3064
__do_sys_mount fs/namespace.c:3078 [inline]
__se_sys_mount fs/namespace.c:3075 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801d7a7fc80
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 288 bytes inside of
512-byte region [ffff8801d7a7fc80, ffff8801d7a7fe80)
The buggy address belongs to the page:
page:ffffea00075e9fc0 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0007616688 ffffea00075d9a88 ffff8801da800940
raw: 0000000000000000 ffff8801d7a7f000 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d7a7fc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801d7a7fd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801d7a7fd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801d7a7fe00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801d7a7fe80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
This bug is generated by a bot. It may contain errors.
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[syzbot]

syzbot has bisected this bug to:

commit 7594bf37ae9ffc434da425120c576909eb33b0bc
Author: Al Viro <vi...@zeniv.linux.org.uk>
Date: Mon Jul 17 02:53:08 2017 +0000

9p: untangle ->poll() mess

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12ad235ee00000
start commit: ca04b3cc Merge tag 'armsoc-fixes' of git://git.kernel.org/..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=11ad235ee00000
console output: https://syzkaller.appspot.com/x/log.txt?x=16ad235ee00000

kernel config: https://syzkaller.appspot.com/x/.config?x=2ca6c7a31d407f86
dashboard link: https://syzkaller.appspot.com/bug?extid=1c9db6a163a4000d0765

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1473a452400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14087748400000

Reported-by: syzbot+1c9db6...@syzkaller.appspotmail.com
Fixes: 7594bf37ae9f ("9p: untangle ->poll() mess")

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

[syzbot]

syzbot suspects this bug was fixed by commit:

commit 430ac66eb4c5b5c4eb846b78ebf65747510b30f1
Author: Tomas Bortoli <tomasb...@gmail.com>
Date: Fri Jul 20 09:27:30 2018 +0000

net/9p/trans_fd.c: fix race-condition by flushing workqueue before the
kfree()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15661282e00000
start commit: ca04b3cc Merge tag 'armsoc-fixes' of git://git.kernel.org/..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=2ca6c7a31d407f86
dashboard link: https://syzkaller.appspot.com/bug?extid=1c9db6a163a4000d0765

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1473a452400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14087748400000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: net/9p/trans_fd.c: fix race-condition by flushing workqueue
before the kfree()

[Tomas Bortoli]

#syz fix: net/9p/trans_fd.c: fix race-condition by flushing workqueue  
before the kfree()

[Eric Biggers]

On Mon, Dec 09, 2019 at 02:59:38PM +0100, Tomas Bortoli wrote:
> #syz fix: net/9p/trans_fd.c: fix race-condition by flushing workqueue
> before the kfree()

Needs to be one line: