Linux could write to read only files on FreeBSD NFS server

[jdelisle]

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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