Description The setuid-root `worker-launcher` binary adjusts ownership and permissions of worker directories by walking the tree with FTS a

Description

The setuid-root worker-launcher binary adjusts ownership and permissions of worker directories by walking
the tree with FTS and calling lchown and chmod on each entry's full pathname while running with an
effective uid of 0. Both syscalls re-resolve the path at the time of the call, after FTS has classified the
entry, and the trees being walked are owned and writable by the untrusted topology user.

A tenant running code on a supervisor node could therefore replace an intermediate directory component with
a symbolic link between classification and the privileged operation, redirecting the root-owned lchown or
chmod at an arbitrary file on the host. The operation is repeatable at will, since crashing a worker
forces a relaunch and blob updates re-run the walk, so a failed attempt costs the attacker nothing.

This crosses the boundary that supervisor.run.worker.as.user and container isolation are intended to
enforce. It is the same defect class as the Hadoop container-executor issues from which this code derives.

Mitigation

Upgrade to 3.1.0, where the privileged walk operates on file descriptors it has already stat'd rather than
on pathnames re-resolved at call time.

Users who cannot upgrade immediately should not run untrusted topology code on supervisors configured with
supervisor.run.worker.as.user, since the launcher is the boundary being crossed. Note that the launcher
must be rebuilt and reinstalled after upgrading; replacing the Java artifacts alone is not sufficient.

Credit

The ASF -- found using Claude agents to study the security of open-source projects, validated and reported by Apache Storm.