linux-kernel - Re: usb/core: warning in usb_create_ep_devs/sysfs_create_dir

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Date:   Tue, 13 Dec 2016 19:44:34 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzkaller <syzkaller@...glegroups.com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kostya Serebryany <kcc@...gle.com>
Subject: Re: usb/core: warning in usb_create_ep_devs/sysfs_create_dir_ns

On Tue, Dec 13, 2016 at 7:38 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> On Tue, 13 Dec 2016, Dmitry Vyukov wrote:
>
>> On Tue, Dec 13, 2016 at 4:52 PM, Alan Stern <stern@...land.harvard.edu> wrote:
>> > On Tue, 13 Dec 2016, Dmitry Vyukov wrote:
>> >
>> >> >> >  If it is
>> >> >> > not a bug in kernel source code, then it must not produce a WARNING.
>> >> >
>> >> > What about a memory allocation failure?  The memory management part of
>> >> > the kernel produces a WARNING message if an allocation fails and the
>> >> > caller did not specify __GFP_NOWARN.
>> >> >
>> >> > There is no way for a driver to guarantee that a memory allocation
>> >> > request will succeed -- failure is always an option.  But obviously
>> >> > memory allocation failures are not bugs in the kernel.
>> >> >
>> >> > Are you saying that mm/page_alloc.c:warn_alloc() should produce
>> >> > something other than a WARNING?
>> >>
>> >>
>> >> The main thing I am saying is that we absolutely need a way for a
>> >> human or a computer program to be able to determine if there is
>> >> anything wrong with kernel or not.
>> > Doesn't it also produce a WARNING under other circumstances?
>>
>> No.
>>
>> OOM is not a WARNING and is easily distinguishable from BUG/WARNING.
>
>> Memory allocator does not print WARNINGs on allocation failures.
>
> Do you count dev_warn the same as WARN or WARN_ON?  What about dev_WARN
> or pr_warn() or printk(KERN_WARNING...)?  Maybe we're not talking about
> the same messages.
>
> The USB subsystem has got tons of dev_warn() and dev_err() calls.
> Relatively few (if any) of them are for kernel bugs.


I grep for "WARNING:". It is not possible to understand what function
printed messages on console.
Here are my current regexps:
https://github.com/google/syzkaller/blob/master/report/report.go#L29