linux-kernel - Re: [PATCH] ubifs: add CONFIG_UBIFS_FS_SECURITY to disable/enable security labels

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Date:   Fri, 03 Mar 2017 19:38:33 +0900
From:   Hyunchul Lee <hyc.lee@...il.com>
To:     Richard Weinberger <richard@....at>
CC:     kernel-team@....com, Artem Bityutskiy <dedekind1@...il.com>,
        adrian.hunter@...el.com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        Hyunchul Lee <cheol.lee@....com>
Subject: Re: [PATCH] ubifs: add CONFIG_UBIFS_FS_SECURITY to disable/enable
 security labels

Hi, Richard

On 03/03/2017 04:56 PM, Richard Weinberger wrote:
> Hyunchul Lee,
> 
> Am 03.03.2017 um 08:44 schrieb Hyunchul Lee:
>> From: Hyunchul Lee <cheol.lee@....com>
>>
>> When write syscall is called, every time security label is searched to
>> determine that file's privileges should be changed.
>> If LSM(Linux Security Model) is not used, this is useless.
>>
>> So introduce CONFIG_UBIFS_SECURITY to disable security labels. it's default
>> value is "y".
> 
> Can you please explain what the benefit is and why UBIFS needs this (and why not
> all other filesystems)?
> I guess some performance issue, do you have numbers?

no, i don't have issues and profile result. but, every time when i write
4KB blocks, ubifs_xattr_get is called with "security.capabilties" for
each 4KB write.  so i think that it is useless if LSM isn't used.

<7>[92028.334484] xattr_get:610: UBIFS DBG gen (pid 25746): xattr 'capability', ino 70 ('rand_5'), buf size 0
<7>[92028.334485] ubifs_lookup_level0:1183: UBIFS DBG tnc (pid 25746): search key (70, xentry, 0x10888ae6)
<7>[92028.334486] ubifs_lookup_level0:1221: UBIFS DBG tnc (pid 25746): found 0, lvl 0, n 6 

and some file system such as ext4 and f2fs have a kernel config to               
disable security labels. (EXT4_FS_SECURITY, F2FS_FS_SECURITY)

> 
> Thanks,
> //richard
> 

Thanks,
Hyunchul