mnt: mount the auto-provisioned /proc nosuid,nodev,noexec#283
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The procfs nsjail auto-mounts (setupMounts) was created without
nosuid/nodev/noexec, so it was mounted dev,suid,exec. Every other
container runtime (runc, Docker, systemd-nspawn) mounts /proc
nosuid,nodev,noexec: there is no legitimate reason for /proc to honor
setuid bits, expose device nodes, or allow execution, and doing so
needlessly widens the in-jail attack surface (e.g. a setuid-root binary
or a device node reachable via a procfs path).
Both mount backends already honor these MountPt fields (mnt_newapi.cc,
mnt_legacy.cc), and the flags remain operator-overridable via an explicit
mount {} config entry.
Verified: /proc inside the jail now shows nosuid,nodev,noexec in
/proc/self/mountinfo (was rw,relatime).
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The procfs nsjail auto-mounts (setupMounts) was created without nosuid/nodev/noexec, so it was mounted dev,suid,exec. Every other container runtime (runc, Docker, systemd-nspawn) mounts /proc nosuid,nodev,noexec: there is no legitimate reason for /proc to honor setuid bits, expose device nodes, or allow execution, and doing so needlessly widens the in-jail attack surface (e.g. a setuid-root binary or a device node reachable via a procfs path).
Both mount backends already honor these MountPt fields (mnt_newapi.cc, mnt_legacy.cc), and the flags remain operator-overridable via an explicit mount {} config entry.
Verified: /proc inside the jail now shows nosuid,nodev,noexec in /proc/self/mountinfo (was rw,relatime).