WARNING: suspicious RCU usage in bpf_prog_array_copy_core

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    4110b42356f3 Add linux-next specific files for 20180810
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=109bac02400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1d80606e3795a4f5
dashboard link: https://syzkaller.appspot.com/bug?extid=6e72317008eef84a216b
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=157ef48a400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12e16cf8400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6e72317008eef84a216b@xxxxxxxxxxxxxxxxxxxxxxxxx

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)

=============================
WARNING: suspicious RCU usage
4.18.0-rc8-next-20180810+ #36 Not tainted
-----------------------------
kernel/bpf/core.c:1582 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-executor287/4449:
 #0: 00000000d8131c0c (&ctx->mutex){+.+.}, at:  
perf_event_ctx_lock_nested+0x375/0x600 kernel/events/core.c:1276
 #1: 000000006c916250 (bpf_event_mutex){+.+.}, at:  
perf_event_query_prog_array+0x1c6/0x380 kernel/trace/bpf_trace.c:1062

stack backtrace:
CPU: 1 PID: 4449 Comm: syz-executor287 Not tainted  
4.18.0-rc8-next-20180810+ #36
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 lockdep_rcu_suspicious+0x14a/0x153 kernel/locking/lockdep.c:4562
 bpf_prog_array_copy_core+0x2d9/0x360 kernel/bpf/core.c:1582
 bpf_prog_array_copy_info+0x9a/0x110 kernel/bpf/core.c:1720
 perf_event_query_prog_array+0x22e/0x380 kernel/trace/bpf_trace.c:1063
 _perf_ioctl+0x986/0x1600 kernel/events/core.c:5079
 perf_ioctl+0x59/0x80 kernel/events/core.c:5110
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
 __do_sys_ioctl fs/ioctl.c:709 [inline]
 __se_sys_ioctl fs/ioctl.c:707 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440409
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffc5fc1488 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440409
RDX: 0000000020000180 RSI: 00000000c008240a RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000217 R12: 0000000000401c90
R13: 0000000000401d20 R14: 0000000000000000


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