linux-kernel - Re: regression: "95cde3c59966 debugfs: inode: debugfs_create_dir uses mode permission from parent" terminally annoys libvirt

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Message-Id: <cba2a66b-e8f7-6bf0-d4c1-8f2ba7d89822@linux.ibm.com>
Date:   Fri, 8 Jun 2018 14:13:57 +0200
From:   Thomas-Mich Richter <tmricht@...ux.ibm.com>
To:     Mike Galbraith <efault@....de>, LKML <linux-kernel@...r.kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: regression: "95cde3c59966 debugfs: inode: debugfs_create_dir uses
 mode permission from parent" terminally annoys libvirt

On 06/08/2018 09:16 AM, Mike Galbraith wrote:
> Greetings,
> 
> $subject bisected and verified via revert.  Box is garden variety
> i4790, distro is openSUSE Leap 15.0.
> 
> Error starting domain: internal error: process exited while connecting to monitor: ioctl(KVM_CREATE_VM) failed: 12 Cannot allocate memory
> 2018-06-08T03:18:00.453006Z qemu-system-x86_64: failed to initialize KVM: Cannot allocate memory
> 
> Traceback (most recent call last):
>   File "/usr/share/virt-manager/virtManager/asyncjob.py", line 89, in cb_wrapper
>     callback(asyncjob, *args, **kwargs)
>   File "/usr/share/virt-manager/virtManager/asyncjob.py", line 125, in tmpcb
>     callback(*args, **kwargs)
>   File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 82, in newfn
>     ret = fn(self, *args, **kwargs)
>   File "/usr/share/virt-manager/virtManager/domain.py", line 1508, in startup
>     self._backend.create()
>   File "/usr/lib64/python3.6/site-packages/libvirt.py", line 1069, in create
>     if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
> libvirt.libvirtError: internal error: process exited while connecting to monitor: ioctl(KVM_CREATE_VM) failed: 12 Cannot allocate memory
> 2018-06-08T03:18:00.453006Z qemu-system-x86_64: failed to initialize KVM: Cannot allocate memory
> 
> 95cde3c59966f6371b6bcd9e4e2da2ba64ee9775 is the first bad commit
> commit 95cde3c59966f6371b6bcd9e4e2da2ba64ee9775
> Author: Thomas Richter <tmricht@...ux.ibm.com>
> Date:   Fri Apr 27 14:35:47 2018 +0200
> 
>     debugfs: inode: debugfs_create_dir uses mode permission from parent
>     
...

Hi,

that patch does not allocate any memory, it just sets permission on newly
created subdirectories in /sys/kernel/debug.
I do not know what ioctl(KVM_CREATE_VM) does, but maybe requires permissions
for group and others in that directory.

Best thing is to revert this patch.

-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
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