I've mounted an iso image as loop device in my linux box on /dev/loop0. I'm also having a network namespace [tmpns] and in my linux box.

When I start a new process to run on tmpns then this mount device is attached to new process"/proc/15350/mounts", but when I try to unmount the loop back device entry for this process is not getting removed from /proc/15350 directory.

I'm not using this mount point "/dev/loop0" inside the network namespace tmpns.

So is there is any way when starting the process I can mention not to mount /dev/loop0 for this new process or is there is any way I can unmount a /dev/loop0 for a particular process.

No way of hiding/unmounting a device just for for one process process. that I am aware of - I see nobody has chimed in on this with better ideas.

I am sure you can make it inaccessible though, by cleverly working on permissions, or some security suite (e.g. Selinux). You can also double mount it, have one for your process, and unmount the second mount later. This sort of thing.

mount /dev/sdaN /here
mount /dev/sda5 /there
<process uses /there, others can access /here>
unmount /there.

creates a loop back device on <mountpoint>
you then
when finished with it.

More correct one would be: