Linux could write to read only files on FreeBSD NFS server

[Luoqi Chen]

I gather you haven't tried the script -- I didn't bother to include more
details because they didn't seem to matter, this is not some corner case
scenario. My guess is this is something fundamental, like, linux expects
the server side to enforce the access control while freebsd assumes that
the client has already done the check.

On Thu, Feb 27, 2020 at 10:40 AM jdelisle <jdelisle at gmail.com> wrote:

> I feel like this is missing a lot of important information needed to
> answer your question.
>
> What's your NFS mount command?  What user are you running that script as?
> What do the permissions look like on the NFS server side?  What does your
> NFS export look like? etc..
>
> On Thu, Feb 27, 2020 at 11:42 AM Luoqi Chen <luoqi.chen at gmail.com> wrote:
>
>> Hi,
>>
>> This was actually a pretty old problem, I noticed it a few years back and
>> have been monitoring it when I upgrade the os on either the linux or the
>> freebsd side -- it's still present between the latest centos and freebsd
>> as
>> of today. I meant to look into this issue myself, but had never found time
>> for it, that's why I'm writing to this list, maybe it's a known problem or
>> someone's willing to spend some time on it.
>>
>> And here you go, the problem,
>>
>> % cat ~/rotest.sh
>> #!/bin/sh
>> cp /dev/null x
>> getfacl x
>> chmod -w x
>> getfacl x
>> echo aaa >> x
>> echo status $?
>> cat x
>> rm -f x
>> % sh ~/rotest.sh
>> # file: x
>> # owner: luoqi
>> # group: wheel
>> user::rw-
>> group::r--
>> other::r--
>>
>> # file: x
>> # owner: luoqi
>> # group: wheel
>> user::r--
>> group::r--
>> other::r--
>>
>> status 0
>> aaa
>>
>> The script was run on a centos inside a directory nfs mounted from a
>> freebsd. The append would fail for a centos/centos or a freebsd/freebsd
>> combo. It's very easy to reproduce, it doesn't depend on any specific
>> centos or freebsd version, nor on nfs version 3 or 4, nor on underlying
>> file system ffs or zfs.
>>
>> -luoqi
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>