On Wed, May 17, 2017 at 8:43 AM, Sebastien Buisson <sbuisson.ddn@xxxxxxxxx> wrote: > 2017-05-17 17:34 GMT+02:00 William Roberts <bill.c.roberts@xxxxxxxxx>: >>>>>> Is there a particular reason to not just return policybrief_len here as >>>>>> well, for consistency in the interface? How do you intend to use this >>>>>> value in the caller? >>>>> >>>>> As called in the other patch to expose policy brief via selinuxfs >>>>> (sel_read_policybrief), the intent is to provide the caller with the >>>>> length of the string returned. >>>>> Or should I set *len to policy brief_len here, and just make the >>>>> caller aware that the returned length is in fact the length of the >>>>> buffer (i.e. including terminating NUL byte)? >>>> >>>> What is the caller supposed to do with length? This interface seemed kind of >>>> odd. If it's guaranteed NUL byte terminated, do they even need length? >>> >>> The length is useful as an input parameter in case the caller provides >>> its own buffer (instead of letting the function allocate one), and as >> >> This is what I don't get, why doesn't the function just always allocate? > > For performance reasons mainly. The caller would have a statically > allocated buffer, reused every time it needs to get the policy brief > info. I'm assuming in the Lustre code you're going to call security_policy_brief(), how would the caller know how big that buffer is going to be? I'm looking at both v5 patches, I don't see where it's being called with alloc set to false. I don't see how this works with LSM stacking, I would imagine the security hook needs to call this routine for each LSM and join them together in some module name spaced way, which was mentioned before, but I don't see that either, am I missing it? -- Respectfully, William C Roberts
