Linux could write to read only files on FreeBSD NFS server

[Luoqi Chen]

On Thu, Feb 27, 2020 at 3:40 PM Alan Batie <alan at peak.org> wrote:

> On 2/27/20 3:31 PM, Luoqi Chen wrote:
>
> > Yes, except to leave the read bit(s) on. I can confirm that the write
> would
> > fail on centos 6/7/8 if all bits are cleared.
> >
>
> That makes no difference:
>
> <zmail03-admin.peak.org> [117] $ sh -x ~/nfst
> + cat /etc/redhat-release
> CentOS release 6.10 (Final)
> + df .
> Filesystem            1K-blocks     Used  Available Use% Mounted on
> zbackups02.peak.org:/zbackups/zmail03-admin
>                      5027215872 91682304 4935533568   2% /zbackups
> + rm -f x
> + touch x
> + chmod 444 x
> + ls -l x
> -r--r--r--. 1 alan root 0 Feb 27 15:38 x
> + echo foo
> /home/alan/nfst: line 9: x: Permission denied
> + cat x
> <zmail03-admin.peak.org> [118] $
>
> Sorry, my mistake, the read bit didn't matter, I mistook the error message
from `cat x` as the echo failure, which I didn't get but you did,

c1n7-154> sh -x rotest.sh
+ cat /etc/redhat-release
CentOS release 6.5 (Final)
+ uname -a
Linux c1n7 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC 2013 x86_64
x86_64 x86_64 GNU/Linux
+ mount
++ df .
++ cut '-d ' -f1
++ tail -1
+ grep c1n5:/data
c1n5:/data on /net/c1n5/data type nfs
(rw,nosuid,nodev,intr,sloppy,vers=4,addr=10.201.2.5,clientaddr=10.201.2.7)
+ rm -f x
+ touch x
+ ls -l x
-rw-r--r--. 1 luoqi wheel 0 Feb 27 17:17 x
+ chmod 0444 x
+ ls -l x
-r--r--r--. 1 luoqi wheel 0 Feb 27 17:17 x
+ echo aaa
+ cat x
aaa
+ rm -f x
+ touch x
+ ls -l x
-rw-r--r--. 1 luoqi wheel 0 Feb 27 17:17 x
+ chmod 0 x
+ ls -l x
----------. 1 luoqi wheel 0 Feb 27 17:17 x
+ echo bbb
+ cat x
cat: x: Permission denied

Another linux machine with the latest centos, same outcome,

c1n14-314> sh -x rotest.sh
+ cat /etc/redhat-release
CentOS Linux release 8.1.1911 (Core)
+ uname -a
Linux c1n14 4.18.0-147.el8.x86_64 #1 SMP Wed Dec 4 21:51:45 UTC 2019 x86_64
x86_64 x86_64 GNU/Linux
+ mount
++ df .
++ tail -1
++ cut '-d ' -f1
+ grep c1n5:/data
c1n5:/data on /net/c1n5/data type nfs4
(rw,nosuid,nodev,relatime,vers=4.1,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=10.201.2.14,local_lock=none,addr=10.201.2.5)
+ rm -f x
+ touch x
+ ls -l x
-rw-r--r--. 1 luoqi wheel 0 Feb 27 17:15 x
+ chmod 0444 x
+ ls -l x
-r--r--r--. 1 luoqi wheel 0 Feb 27 17:15 x
+ echo aaa
+ cat x
aaa
+ rm -f x
+ touch x
+ ls -l x
-rw-r--r--. 1 luoqi wheel 0 Feb 27 17:15 x
+ chmod 0 x
+ ls -l x
----------. 1 luoqi wheel 0 Feb 27 17:15 x
+ echo bbb
+ cat x
cat: x: Permission denied

The freebsd server is running,

c1n5-45> uname -a
FreeBSD c1n5 12.1-RELEASE-p1 FreeBSD 12.1-RELEASE-p1 GENERIC  amd64