WARNING: suspicious RCU usage in qrtr_ns_worker

WARNING: suspicious RCU usage in qrtr_ns_worker

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123db429100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=be4578b3f1083656
dashboard link: https://syzkaller.appspot.com/bug?extid=0f84f6eed90503da72fc
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1521944d100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1298d245100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0f84f6eed90503da72fc@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
5.7.0-syzkaller #0 Not tainted
-----------------------------
include/linux/radix-tree.h:176 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
2 locks held by kworker/u4:1/21:
 #0: ffff88821b097938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: spin_unlock_irq include/linux/spinlock.h:403 [inline]
 #0: ffff88821b097938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: process_one_work+0x6df/0xfd0 kernel/workqueue.c:2241
 #1: ffffc90000dd7d80 ((work_completion)(&qrtr_ns.work)){+.+.}-{0:0}, at: process_one_work+0x71e/0xfd0 kernel/workqueue.c:2243

stack backtrace:
CPU: 0 PID: 21 Comm: kworker/u4:1 Not tainted 5.7.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: qrtr_ns_handler qrtr_ns_worker
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1e9/0x30e lib/dump_stack.c:118
 radix_tree_deref_slot include/linux/radix-tree.h:176 [inline]
 ctrl_cmd_new_lookup net/qrtr/ns.c:558 [inline]
 qrtr_ns_worker+0x2aff/0x4500 net/qrtr/ns.c:674
 process_one_work+0x76e/0xfd0 kernel/workqueue.c:2268
 worker_thread+0xa7f/0x1450 kernel/workqueue.c:2414
 kthread+0x353/0x380 kernel/kthread.c:268


---
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Re: WARNING: suspicious RCU usage in qrtr_ns_worker

[syzbot]

syzbot has bisected this bug to:

commit e42671084361302141a09284fde9bbc14fdd16bf
Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Date:   Thu May 7 12:53:06 2020 +0000

    net: qrtr: Do not depend on ARCH_QCOM

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=105f7755100000
start commit:   7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree:       upstream
final crash:    https://syzkaller.appspot.com/x/report.txt?x=125f7755100000
console output: https://syzkaller.appspot.com/x/log.txt?x=145f7755100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=be4578b3f1083656
dashboard link: https://syzkaller.appspot.com/bug?extid=0f84f6eed90503da72fc
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1521944d100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1298d245100000

Reported-by: syzbot+0f84f6eed90503da72fc@syzkaller.appspotmail.com
Fixes: e42671084361 ("net: qrtr: Do not depend on ARCH_QCOM")

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