netdev - Re: WARNING in tracing_func

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Message-ID: <20200121180255.1c98b54c@gandalf.local.home>
Date:   Tue, 21 Jan 2020 18:02:55 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     syzbot <syzbot+0c147ca7bd4352547635@...kaller.appspotmail.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: WARNING in tracing_func_proto

On Fri, 17 Jan 2020 23:47:11 -0800
syzbot <syzbot+0c147ca7bd4352547635@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    428cd523 sfc/ethtool_common: Make some function to static
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10483421e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=66d8660c57ff3c98
> dashboard link: https://syzkaller.appspot.com/bug?extid=0c147ca7bd4352547635
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+0c147ca7bd4352547635@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> Could not allocate percpu trace_printk buffer
> WARNING: CPU: 1 PID: 11733 at kernel/trace/trace.c:3112 alloc_percpu_trace_buffer kernel/trace/trace.c:3112 [inline]
> WARNING: CPU: 1 PID: 11733 at kernel/trace/trace.c:3112 trace_printk_init_buffers+0x5b/0x60 kernel/trace/trace.c:3126
> Kernel panic - not syncing: panic_on_warn set ...

So it failed to allocate memory for the buffer (must be running low on
memory, or allocated a really big buffer?), and that triggered a
warning. As you have "panic_on_warn" set, the warning triggered the
panic.

The only solution to this that I can see is to remove the WARN_ON and
replace it with a pr_warn() message. There's a lot of WARN_ON()s in the
kernel that need this conversion too, and I will postpone this change
to that effort.

-- Steve


> CPU: 1 PID: 11733 Comm: syz-executor.2 Not tainted 5.5.0-rc5-syzkaller #0
> 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+0x197/0x210 lib/dump_stack.c:118
>  panic+0x2e3/0x75c kernel/panic.c:221
>  __warn.cold+0x2f/0x3e kernel/panic.c:582
>  report_bug+0x289/0x300 lib/bug.c:195
>  fixup_bug arch/x86/kernel/traps.c:174 [inline]
>  fixup_bug arch/x86/kernel/traps.c:169 [inline]
>  do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
>  do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
>  invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
> RIP: 0010:alloc_percpu_trace_buffer kernel/trace/trace.c:3112 [inline]
> RIP: 0010:trace_printk_init_buffers+0x5b/0x60 kernel/trace/trace.c:3126
> Code: ff be 04 00 00 00 bf 04 10 00 00 e8 3f 84 24 00 48 85 c0 0f 85 e8 37 00 00 e8 d1 57 fb ff 48 c7 c7 e0 92 2f 88 e8 54 07 cc ff <0f> 0b eb c2 90 55 48 89 e5 41 57 49 c7 c7 e0 79 2f 88 41 56 49 89
> RSP: 0018:ffffc900018e7528 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 00000000000070cd RSI: ffffffff815e5e56 RDI: fffff5200031ce97
> RBP: ffffc900018e7538 R08: ffff8880a204c3c0 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff88309580
> R13: ffffffff88309240 R14: 0000000000000006 R15: ffff88805a52c000
>  bpf_get_trace_printk_proto kernel/trace/bpf_trace.c:457 [inline]
>  tracing_func_proto.isra.0+0x150/0x1a0 kernel/trace/bpf_trace.c:794
>  pe_prog_func_proto+0x69/0x90 kernel/trace/bpf_trace.c:1023
>  check_helper_call+0x123/0x48f0 kernel/bpf/verifier.c:4196
>  do_check+0x613a/0x8a40 kernel/bpf/verifier.c:7978
>  bpf_check+0x73d9/0xa9ef kernel/bpf/verifier.c:9777
>  bpf_prog_load+0xe36/0x1960 kernel/bpf/syscall.c:1837
>  __do_sys_bpf+0xa4b/0x3610 kernel/bpf/syscall.c:3073
>  __se_sys_bpf kernel/bpf/syscall.c:3032 [inline]
>  __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:3032
>  do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x45af49
> Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f31faef6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045af49
> RDX: 0000000000000048 RSI: 0000000020000080 RDI: 0000000000000005
> RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f31faef76d4
> R13: 00000000004c1697 R14: 00000000004d66a0 R15: 00000000ffffffff
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
>