From: Y Song <ys114321@gmail.com>
To: syzbot <syzbot+6e72317008eef84a216b@syzkaller.appspotmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
LKML <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
syzkaller-bugs@googlegroups.com
Subject: Re: WARNING: suspicious RCU usage in bpf_prog_array_copy_core
Date: Tue, 14 Aug 2018 08:59:04 -0700 [thread overview]
Message-ID: <CAH3MdRWZHkpTq+Pr5Fe6bcEYpYGOhyrfHLd6rjf3s66wr+aR+w@mail.gmail.com> (raw)
In-Reply-To: <000000000000863a6e057361feb4@google.com>
On Tue, Aug 14, 2018 at 2:40 AM, syzbot
<syzbot+6e72317008eef84a216b@syzkaller.appspotmail.com> wrote:
> 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@syzkaller.appspotmail.com
>
> 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
>
I will take a look at this one.
We have a mutex lock at kernel/trace/bpf_trace.c,
1062 mutex_lock(&bpf_event_mutex);
1063 ret = bpf_prog_array_copy_info(event->tp_event->prog_array,
1064 ids,
1065 ids_len,
1066 &prog_cnt);
1067 mutex_unlock(&bpf_event_mutex);
We may need a variant of rcu_dereference, e.g., rcu_dereference_protected.
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
prev parent reply other threads:[~2018-08-14 15:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-14 9:40 WARNING: suspicious RCU usage in bpf_prog_array_copy_core syzbot
2018-08-14 15:59 ` Y Song [this message]
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