Linux could write to read only files on FreeBSD NFS server

[Alan Batie]

On 2/27/20 2:58 PM, Luoqi Chen wrote:
> One more piece of information that might help: this behavior started
> somewhere between centos 5 and 6, kernel 2.6.18 and 2.6.32, i.e., the same
> script would fail on 2.6.18. Timing wise I believe it coincided with the
> introduction of nfsv4.
> 
> Even if this is a linux bug, given its dominant position, we don't have
> much of a choice but to try to be compatible. Does anyone have say access
> to a netapp and see how it behaves?

Is this what you mean?

<admin03.peak.org> [101] $ df .
Filesystem           1K-blocks     Used Available Use% Mounted on
filer01-cvo.peak.org:/vol/admin
                     167772160 73704064  94068096  44% /filer01/cvo-admin
<admin03.peak.org> [102] $ rm -f x
<admin03.peak.org> [103] $ touch x
<admin03.peak.org> [104] $ chmod 000 x
<admin03.peak.org> [105] $ ls -l x
----------. 1 alan wheel 0 Feb 27 15:01 x
<admin03.peak.org> [106] $ echo foo > x
-bash: x: Permission denied
<admin03.peak.org> [107] $ chmod 600 x
<admin03.peak.org> [108] $ cat x
<admin03.peak.org> [109] $ cat /etc/redhat-release
CentOS release 6.10 (Final)


This works the same way on a truenas server:

<admin03.peak.org> [122] $ rm x
<admin03.peak.org> [123] $ df .
Filesystem             1K-blocks     Used   Available Use% Mounted on
tnas01-cvo.fs10g.peak.org:/mnt/zdata/nfs/admin
                     78257431296 54539008 78202892288   1% /tnas01-cvo/admin
<admin03.peak.org> [124] $ touch x
<admin03.peak.org> [125] $ chmod 000 x
<admin03.peak.org> [126] $ ls -l x
----------. 1 alan wheel 0 Feb 27 15:05 x
<admin03.peak.org> [127] $ echo foo > x
-bash: x: Permission denied
<admin03.peak.org> [128] $ chmod 600 x
<admin03.peak.org> [129] $ cat x
<admin03.peak.org> [130] $

However it also does the same on a native FreeBSD 11 server:

<zbackups02.peak.org> [116] $ uname -a
FreeBSD zbackups02.peak.org 11.3-RELEASE-p3 FreeBSD 11.3-RELEASE-p3 #0:
Mon Aug 19 21:08:43 UTC 2019
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64

<zmail03-admin.peak.org> [105] $ cat /etc/redhat-release
CentOS release 6.10 (Final)
<zmail03-admin.peak.org> [106] $ df .
Filesystem            1K-blocks     Used  Available Use% Mounted on
zbackups02.peak.org:/zbackups/zmail03-admin
                     5039303296 91682304 4947620992   2% /zbackups
<zmail03-admin.peak.org> [107] $ touch x
<zmail03-admin.peak.org> [108] $ chmod 0 x
<zmail03-admin.peak.org> [109] $ ls -l x
----------. 1 alan root 0 Feb 27 15:08 x
<zmail03-admin.peak.org> [110] $ echo foo > x
-bash: x: Permission denied
<zmail03-admin.peak.org> [111] $ chmod 600 x
<zmail03-admin.peak.org> [112] $ cat x

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