=============================
WARNING: suspicious RCU usage
5.9.0-rc5-next-20200921-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/u4:0/28114:
 #0: ffff8880a91c9938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff8880a91c9938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff8880a91c9938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff8880a91c9938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
 #0: ffff8880a91c9938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0: ffff8880a91c9938 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: process_one_work+0x821/0x15a0 kernel/workqueue.c:2240
 #1: ffffc90005717da8 ((work_completion)(&qrtr_ns.work)){+.+.}-{0:0}, at: process_one_work+0x854/0x15a0 kernel/workqueue.c:2244

stack backtrace:
CPU: 1 PID: 28114 Comm: kworker/u4:0 Not tainted 5.9.0-rc5-next-20200921-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+0x198/0x1fb lib/dump_stack.c:118
 radix_tree_deref_slot include/linux/radix-tree.h:176 [inline]
 radix_tree_deref_slot include/linux/radix-tree.h:174 [inline]
 ctrl_cmd_new_lookup+0x6d4/0x7c0 net/qrtr/ns.c:558
 qrtr_ns_worker+0x5ca/0x1430 net/qrtr/ns.c:674
 process_one_work+0x933/0x15a0 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3af/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
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