[kernel-hardening] [PATCHv4 1/2] capability: introduce sysctl for controlled user-ns capability whitelist

From: Mahesh Bandewar <redacted>

The default value set (for kernel.controlled_userns_caps_whitelist) is
CAP_FULL_SET indicating that no capability is controlled by default to
maintain compatibility with the existing behavior of user-ns. Administrator
will have to modify this sysctl to control any capability as such. e.g. to
control CAP_NET_RAW the mask need to be changed like -

  # sysctl -q kernel.controlled_userns_caps_whitelist
  kernel.controlled_userns_caps_whitelist = 1f,ffffffff
  # sysctl -w kernel.controlled_userns_caps_whitelist=1f,ffffdfff
  kernel.controlled_userns_caps_whitelist = 1f,ffffdfff

For bit-to-mask conversion please check include/uapi/linux/capability.h
file.

Is it possible to make those sysctl values human readable? That would make
admins life easier.

Yours sincerely

G. K.
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