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

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Date:   Sun, 17 Dec 2017 18:30:28 +0000
From:   Bronek Kozicki <brok@...orrekt.com>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Cc:     cgroups@...r.kernel.org
Subject: Re: PROBLEM: NULL pointer dereference in kernel 4.14.6

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.


B.