This is a fix to the following issue:
$ docker run --tmpfs /dev/shm busybox sh
docker: Error response from daemon: linux mounts: Duplicate mount point '/dev/shm'.
In current code (daemon.createSpec()), tmpfs mount from --tmpfs is added
to list of mounts (`ms`), when the mount from IpcMounts() is added.
While IpcMounts() is checking for existing mounts first, it does that
by using container.HasMountFor() function which only checks container.Mounts
but not container.Tmpfs.
Ultimately, the solution is to get rid of container.Tmpfs (moving its
data to container.Mounts). Current workaround is to add checking
of container.Tmpfs into container.HasMountFor().
A unit test case is included.
Unfortunately we can't call daemon.createSpec() from a unit test,
as the code relies a lot on various daemon structures to be initialized
properly, and it is hard to achieve. Therefore, we minimally mimick
the code flow of daemon.createSpec() -- barely enough to reproduce
the issue.
https://github.com/moby/moby/issues/35455
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
