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SubjectRe: [PATCH 1/2] file capabilities: add no_file_caps switch (v2)
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Acked-by: Andrew G. Morgan <>



Serge Hallyn wrote:
| Add a no_file_caps boot option when file capabilities are
| compiled into the kernel (CONFIG_SECURITY_FILE_CAPABILITIES=y).
| This allows distributions to ship a kernel with file capabilities
| compiled in, without forcing users to use (and understand and
| trust) them.
| When no_file_caps is specified at boot, then when a process executes
| a file, any file capabilities stored with that file will not be
| used in the calculation of the process' new capability sets.
| This means that booting with the no_file_caps boot option will
| not be the same as booting a kernel with file capabilities
| compiled out - in particular a task with CAP_SETPCAP will not
| have any chance of passing capabilities to another task (which
| isn't "really" possible anyway, and which may soon by killed
| altogether by David Howells in any case), and it will instead
| be able to put new capabilities in its pI. However since fI
| will always be empty and pI is masked with fI, it gains the
| task nothing.
| We also support the extra prctl options, setting securebits and
| dropping capabilities from the per-process bounding set.
| The other remaining difference is that killpriv, task_setscheduler,
| setioprio, and setnice will continue to be hooked. That will
| be noticable in the case where a root task changed its uid
| while keeping some caps, and another task owned by the new uid
| tries to change settings for the more privileged task.
| Signed-off-by: Serge Hallyn <>
| ---
| include/linux/capability.h | 4 ++++
| kernel/capability.c | 11 +++++++++++
| security/commoncap.c | 9 +++++++++
| 3 files changed, 24 insertions(+), 0 deletions(-)
| diff --git a/include/linux/capability.h b/include/linux/capability.h
| index 9d1fe30..c96c455 100644
| --- a/include/linux/capability.h
| +++ b/include/linux/capability.h
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