===============================
[ INFO: suspicious RCU usage. ]
4.9.202+ #0 Not tainted
-------------------------------
include/linux/radix-tree.h:199 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
2 locks held by syz-executor.0/20947:
 #0:  (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<00000000fac5d9e2>] inode_lock include/linux/fs.h:771 [inline]
 #0:  (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<00000000fac5d9e2>] shmem_add_seals+0x166/0x1020 mm/shmem.c:2610
 #1:  (&(&mapping->tree_lock)->rlock){..-...}, at: [<00000000fcc88e30>] spin_lock_irq include/linux/spinlock.h:332 [inline]
 #1:  (&(&mapping->tree_lock)->rlock){..-...}, at: [<00000000fcc88e30>] shmem_tag_pins mm/shmem.c:2465 [inline]
 #1:  (&(&mapping->tree_lock)->rlock){..-...}, at: [<00000000fcc88e30>] shmem_wait_for_pins mm/shmem.c:2506 [inline]
 #1:  (&(&mapping->tree_lock)->rlock){..-...}, at: [<00000000fcc88e30>] shmem_add_seals+0x342/0x1020 mm/shmem.c:2622

stack backtrace:
CPU: 0 PID: 20947 Comm: syz-executor.0 Not tainted 4.9.202+ #0
 ffff8801aca27ca0 ffffffff81b55d2b ffff8801c9cf1628 0000000000000000
 0000000000000002 00000000000000c7 ffff8801aff8df00 ffff8801aca27cd0
 ffffffff81406867 ffffea0006481c00 dffffc0000000000 ffff8801aca27d78
Call Trace:
 [<00000000ae2de0ba>] __dump_stack lib/dump_stack.c:15 [inline]
 [<00000000ae2de0ba>] dump_stack+0xcb/0x130 lib/dump_stack.c:56
 [<00000000b139d762>] lockdep_rcu_suspicious.cold+0x10a/0x149 kernel/locking/lockdep.c:4458
 [<00000000ae941f50>] radix_tree_deref_slot include/linux/radix-tree.h:199 [inline]
 [<00000000ae941f50>] shmem_tag_pins mm/shmem.c:2467 [inline]
 [<00000000ae941f50>] shmem_wait_for_pins mm/shmem.c:2506 [inline]
 [<00000000ae941f50>] shmem_add_seals+0xa44/0x1020 mm/shmem.c:2622
 [<0000000000fe5da6>] shmem_fcntl+0xf7/0x130 mm/shmem.c:2657
 [<00000000da8bd76b>] do_fcntl fs/fcntl.c:340 [inline]
 [<00000000da8bd76b>] SYSC_fcntl fs/fcntl.c:376 [inline]
 [<00000000da8bd76b>] SyS_fcntl+0x1d5/0xb50 fs/fcntl.c:361
 [<000000009b60bc88>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<00000000eee94751>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb