netdev - Re: WARNING in tracing_func

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Date:   Wed, 22 Jan 2020 08:53:15 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     syzbot <syzbot+0c147ca7bd4352547635@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: WARNING in tracing_func_proto

On Tue, Jan 21, 2020 at 06:02:55PM -0500, Steven Rostedt wrote:
> 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.
> 

I bet the syzbot folk have changed to lot of WARN_ON()s.  Maybe they
just comment them out on their local tree?

regards,
dan carpenter