netdev - Re: memory leak in kobject_set_name

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Message-Id: <E20E1982-1F60-4F01-AE3C-0CF397A596C4@lca.pw>
Date:   Fri, 26 Jul 2019 22:56:19 -0400
From:   Qian Cai <cai@....pw>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     syzbot <syzbot+ad8ca40ecd77896d51e2@...kaller.appspotmail.com>,
        Catalin Marinas <catalin.marinas@....com>,
        David Miller <davem@...emloft.net>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>, kuznet@....inr.ac.ru,
        Kalle Valo <kvalo@...eaurora.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, luciano.coelho@...el.com,
        Netdev <netdev@...r.kernel.org>, steffen.klassert@...unet.com,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        yoshfuji@...ux-ipv6.org, Wang Hai <wanghai26@...wei.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: memory leak in kobject_set_name_vargs (2)



> On Jul 26, 2019, at 10:29 PM, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> On Fri, Jul 26, 2019 at 4:26 PM syzbot
> <syzbot+ad8ca40ecd77896d51e2@...kaller.appspotmail.com> wrote:
>> 
>> syzbot has bisected this bug to:
>> 
>> commit 0e034f5c4bc408c943f9c4a06244415d75d7108c
>> Author: Linus Torvalds <torvalds@...ux-foundation.org>
>> Date:   Wed May 18 18:51:25 2016 +0000
>> 
>>     iwlwifi: fix mis-merge that breaks the driver
> 
> While this bisection looks more likely than the other syzbot entry
> that bisected to a version change, I don't think it is correct eitger.
> 
> The bisection ended up doing a lot of "git bisect skip" because of the
> 
>    undefined reference to `nf_nat_icmp_reply_translation'
> 
> issue. Also, the memory leak doesn't seem to be entirely reliable:
> when the bisect does 10 runs to verify that some test kernel is bad,
> there are a couple of cases where only one or two of the ten run
> failed.
> 
> Which makes me wonder if one or two of the "everything OK" runs were
> actually buggy, but just happened to have all ten pass…

Real bisection should point to,

8ed633b9baf9e (“Revert "net-sysfs: Fix memory leak in netdev_register_kobject”")

I did encounter those memory leak and comes up with a similar fix in,

6b70fc94afd1 ("net-sysfs: Fix memory leak in netdev_register_kobject”)

but those error handling paths are tricky that seems nobody did much testing there, so it will
keep hitting other bugs in upper functions.