capabilites: allow the application of capability limits to usermode helpers

There is no way to limit the capabilities of usermodehelpers. This problem
reared its head recently when someone complained that any user with
cap_net_admin was able to load arbitrary kernel modules, even though the user
didn't have cap_sys_module.  The reason is because the actual load is done by
a usermode helper and those always have the full cap set.  This patch addes new
sysctls which allow us to bound the permissions of usermode helpers.

/proc/sys/kernel/usermodehelper/bset
/proc/sys/kernel/usermodehelper/inheritable

You must have CAP_SYS_MODULE  and CAP_SETPCAP to change these (changes are
&= ONLY).  When the kernel launches a usermodehelper it will do so with these
as the bset and pI.

-v2:	make globals static
	create spinlock to protect globals

-v3:	require both CAP_SETPCAP and CAP_SYS_MODULE
-v4:	fix the typo s/CAP_SET_PCAP/CAP_SETPCAP/ because I didn't commit
Signed-off-by: Eric Paris <[email protected]>
No-objection-from: Serge E. Hallyn <[email protected]>
Acked-by: David Howells <[email protected]>
Acked-by: Serge E. Hallyn <[email protected]>
Acked-by: Andrew G. Morgan <[email protected]>
Signed-off-by: James Morris <[email protected]>

0 files changed, 0 insertions, 0 deletions