netdev - Re: dangers of bots on the mailing lists was Re: divide error in ___bpf_prog

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Message-ID: <20180118014645.66zlrz3bma6wc4xl@gmail.com>
Date:   Wed, 17 Jan 2018 17:46:45 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Theodore Ts'o <tytso@....edu>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Pavel Machek <pavel@....cz>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: dangers of bots on the mailing lists was Re: divide error in
 ___bpf_prog_run

On Wed, Jan 17, 2018 at 05:18:17PM -0800, Joe Perches wrote:
> On Wed, 2018-01-17 at 20:09 -0500, Theodore Ts'o wrote:
> > get_maintainer.pl, which is often not accurate
> 
> Examples please.
> 

Well, the primary problem is that place the crash occurs is not necessarily
responsible for the bug.  But, syzbot actually does have a file blacklist for
exactly that reason; see
https://github.com/google/syzkaller/blob/master/pkg/report/linux.go#L56

It definitely needs further improvement (and anyone is welcome to contribute),
though it will never be perfect.  

There is also a KASAN change by Dmitry queued up for 4.16 that will allow KASAN
to detect invalid frees.  That would have detected the bug in crypto/pcrypt.c
that was causing corruption in the kmalloc-1024 slab cache, and was causing
crashes in all sorts of random kernel code, resulting many bug reports.  So,
detecting bugs early before they corrupt all sorts of random kernel data
structures helps a lot too.

And yes, get_maintainer.pl sometimes isn't accurate even if the offending code
is correctly identified.  That's more of a community problem, e.g. people
sometimes don't bother to remove themselves from MAINTAINERS when they quit
maintaining, and sometimes people don't feel responsible enough for a file to
add themselves to MAINTAINERS, even when in practice they are actually taking
most of the patches to it through their tree.

Eric