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    SubjectRe: [PATCH] capabilities: introduce per-process capability bounding set (v10)
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    KaiGai Kohei wrote:
    > Serge,
    >
    > Please tell me the meanings of the following condition.
    >
    >> diff --git a/security/commoncap.c b/security/commoncap.c
    >> index 3a95990..cb71bb0 100644
    >> --- a/security/commoncap.c
    >> +++ b/security/commoncap.c
    >> @@ -133,6 +119,12 @@ int cap_capset_check (struct task_struct *target,
    >> kernel_cap_t *effective,
    >> /* incapable of using this inheritable set */
    >> return -EPERM;
    >> }
    >> + if (!!cap_issubset(*inheritable,
    >> + cap_combine(target->cap_inheritable,
    >> + current->cap_bset))) {
    >> + /* no new pI capabilities outside bounding set */
    >> + return -EPERM;
    >> + }
    >>
    >> /* verify restrictions on target's new Permitted set */
    >> if (!cap_issubset (*permitted,
    >
    > It seems to me this condition requires the new inheritable capability
    > set must have a capability more than bounding set, at least.
    > What is the purpose of this checking?

    Yes, the !! was a bug. The correct check is a single !.

    (Thus, the correct check says no 'new' pI bits can be outside cap_bset.)

    Cheers

    Andrew

    >
    > In the initial state, any process have no inheritable capability set
    > and full bounding set. Thus, we cannot do capset() always.
    >
    > Thanks,

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