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From: haosdent <haosdent@gmail.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	zhengyu.duan@shopee.com, Haosong Huang <huangh@sea.com>
Subject: Re: NULL pointer dereference when access /proc/net
Date: Mon, 26 Apr 2021 01:04:46 +0800	[thread overview]
Message-ID: <CAFt=RONcpvvk5=8GLTvG44=6wKwiYPH7oG4YULfcP+J=x8OW-w@mail.gmail.com> (raw)
In-Reply-To: <YIWd7v1U/dGivmSE@zeniv-ca.linux.org.uk>

Hi, Alexander, thanks a lot for your quick reply.

> Not really - the crucial part is ->d_count == -128, i.e. it's already past
> __dentry_kill().

Thanks a lot for your information, we would check this.

> Which tree is that?
> If you have some patches applied on top of that...

We use Ubuntu Linux Kernel "4.15.0-42.45~16.04.1" from launchpad directly
without any modification,  the mapping Linux Kernel should be
"4.15.18" according
to https://people.canonical.com/~kernel/info/kernel-version-map.html

On Mon, Apr 26, 2021 at 12:50 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Sun, Apr 25, 2021 at 11:22:15PM +0800, haosdent wrote:
> > Hi, Alexander Viro and dear Linux Filesystems maintainers, recently we
> > encounter a NULL pointer dereference Oops in our production.
> >
> > We have attempted to analyze the core dump and compare it with source code
> > in the past few weeks, currently still could not understand why
> > `dentry->d_inode` become NULL while other fields look normal.
>
> Not really - the crucial part is ->d_count == -128, i.e. it's already past
> __dentry_kill().
>
> > [19521409.514784] RIP: 0010:__atime_needs_update+0x5/0x190
>
> Which tree is that?  __atime_needs_update() had been introduced in
> 4.8 and disappeared in 4.18; anything of that age straight on mainline
> would have a plenty of interesting problems.  If you have some patches
> applied on top of that...  Depends on what those are, obviously.



-- 
Best Regards,
Haosdent Huang

  reply	other threads:[~2021-04-25 17:05 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAFt=RON+KYYf5yt9vM3TdOSn4zco+3XtFyi3VDRr1vbQUBPZ0g@mail.gmail.com>
2021-04-25 16:50 ` NULL pointer dereference when access /proc/net Al Viro
2021-04-25 17:04   ` haosdent [this message]
2021-04-25 17:14     ` haosdent
2021-04-25 17:22     ` Al Viro
2021-04-25 18:00       ` haosdent
2021-04-25 18:15         ` haosdent
2021-04-26 17:16       ` haosdent
2021-04-26 17:30         ` Al Viro
2021-05-03 15:31           ` haosdent
2021-05-06 10:21             ` haosdent
2021-04-25 15:47 haosdent

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