syzbot

random: sshd: uninitialized urandom read (32 bytes read)
audit: type=1400 audit(1572790266.538:36): avc:  denied  { map } for  pid=6845 comm="syz-executor220" path="/root/syz-executor220679597" dev="sda1" ino=16483 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
=============================
WARNING: suspicious RCU usage
4.14.151 #0 Not tainted
-----------------------------
./include/linux/radix-tree.h:238 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
2 locks held by syz-executor220/6845:
 #0:  (&sb->s_type->i_mutex_key#12){+.+.}, at: [<ffffffff81770c7e>] inode_lock include/linux/fs.h:718 [inline]
 #0:  (&sb->s_type->i_mutex_key#12){+.+.}, at: [<ffffffff81770c7e>] shmem_add_seals+0x15e/0x1060 mm/shmem.c:2810
 #1:  (&(&mapping->tree_lock)->rlock){-...}, at: [<ffffffff81770e54>] spin_lock_irq include/linux/spinlock.h:342 [inline]
 #1:  (&(&mapping->tree_lock)->rlock){-...}, at: [<ffffffff81770e54>] shmem_tag_pins mm/shmem.c:2665 [inline]
 #1:  (&(&mapping->tree_lock)->rlock){-...}, at: [<ffffffff81770e54>] shmem_wait_for_pins mm/shmem.c:2706 [inline]
 #1:  (&(&mapping->tree_lock)->rlock){-...}, at: [<ffffffff81770e54>] shmem_add_seals+0x334/0x1060 mm/shmem.c:2822

stack backtrace:
CPU: 0 PID: 6845 Comm: syz-executor220 Not tainted 4.14.151 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x138/0x197 lib/dump_stack.c:53
 lockdep_rcu_suspicious+0x153/0x15d kernel/locking/lockdep.c:4665
 radix_tree_deref_slot include/linux/radix-tree.h:238 [inline]
 radix_tree_deref_slot include/linux/radix-tree.h:236 [inline]
 shmem_tag_pins mm/shmem.c:2667 [inline]
 shmem_wait_for_pins mm/shmem.c:2706 [inline]
 shmem_add_seals+0x9e0/0x1060 mm/shmem.c:2822
 shmem_fcntl+0xf7/0x130 mm/shmem.c:2857
 do_fcntl+0x190/0xe10 fs/fcntl.c:421
 SYSC_fcntl fs/fcntl.c:463 [inline]
 SyS_fcntl+0xd5/0x110 fs/fcntl.c:448
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4401b9
RSP: 002b:00007ffeb3400b68 EFLAGS: 00000246 ORIG_RAX: 000