linux-kernel - Re: PROBLEM: NULL pointer dereference in kernel 4.14.6

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Message-ID: <ec8d36ae-4fd6-a71c-0eb6-2d36e3d331ae@infradead.org>
Date:   Sun, 17 Dec 2017 10:31:39 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Bronek Kozicki <brok@...orrekt.com>, linux-kernel@...r.kernel.org
Cc:     cgroups@...r.kernel.org
Subject: Re: PROBLEM: NULL pointer dereference in kernel 4.14.6

On 12/17/2017 10:30 AM, Bronek Kozicki wrote:
> On 17/12/2017 18:25, Randy Dunlap wrote:
>> On 12/17/2017 09:49 AM, Bronek Kozicki wrote:
>>> I just upgraded to 4.14.7 and tried to reproduce this error, this time under strace. As you can see this happens when systemctl tries to read a specific entry under /sys/fs . In case this matters, the entry is for a small virtual machine running under qemu/kvm and managed by libvirt.
>>>
>>> open("/sys/fs/cgroup/unified/machine.slice", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
>>> fstat(5, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
>>> getdents(5, /* 12 entries */, 32768)    = 464
>>> openat(AT_FDCWD, "/sys/fs/cgroup/unified/machine.slice/machine-qemu\\x2d1\\x2dkartuzy\\x2dspice.scope/cgroup.procs", O_RDONLY|O_CLOEXEC) = 8
>>> fstat(8, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
>>> read(8,  <unfinished ...>)              = ?
>>> +++ killed by SIGKILL +++
>>> [1]    12078 killed     strace -- systemctl status
>>>
>>>
>>> B.
>>>
>>
>> Hi,
>>
>> Can you reproduce this without using (loading) the XFS modules?
>> They cause the kernel to be tainted.
> 
> I think you mean ZFS - I cannot do that. It is my root filesystem.

Sorry, yes, I did mean ZFS.

thanks,
-- 
~Randy