On Wed, Jun 27, 2001 at 02:52:17PM +0200, Marcus Brinkmann wrote:
[auth_getids]
> This one is questionable. auth_getids uses idvec_copyout, which provides
> the internal buffer:
>
> inline void idvec_copyout (struct idvec *idvec, uid_t **ids, uid_t *nids)
> {
> if (idvec->num > *nids)
> *ids = idvec->ids;
> else
> memcpy (*ids, idvec->ids, idvec->num * sizeof *ids);
> *nids = idvec->num;
> }
>
> So, this should not use dealloc. However, idvec->ids is NOT a mmap'ed
> buffer! It is a malloced/realloced buffer (coming from
> libshouldbeinlibc/idvec.c). Also, the code should not use
> sizeof *ids, but sizeof (uid_t) = sizeof **ids for the calculation!
>
> Is it correct that this should better use iohelp_return_malloced_buffer
> and dealloc or mmap in idvec.h for the performance?
I would suggest dealloc + iohelp_return_malloced_buffer, as usually those
uid vectors are small, and keeping them on one page each is a waste of
space.
> > routine auth_server_authenticate (
[...]
> Again, I am not sure. The server routine has:
>
> /* Extract the ids. We must use a separate reply stub so
> we can deref the user auth handle after the reply uses its
> contents. */
> auth_server_authenticate_reply (reply, reply_type, 0,
> user->euids.ids, user->euids.num,
> user->auids.ids, user->auids.num,
> user->egids.ids, user->egids.num,
> user->agids.ids, user->agids.num);
> ports_port_deref (user);
>
> Because those arrays are not marked as dealloc, the pointer is copied by
> the reply stub. Again, we are returning malloc'ed buffers. But this time
> we are returning buffers without keeping a reference to them! The comment
> is actually useless, as the buffers are not copied. Am I incorrect, or is
> this a blatant error?
I was incorrect, I think. Small uid vectors are copied in the message
inlined, while out-of-band memory is logically copied. Although the
physical page is shared, it will not be removed unless the server and client
both called vm_deallocate on it (if I understood this correctly).
> It seems that using return-buffer and dealloc is the only chance, if we
> don't want to giver the server a reference to the user.
Not in this case. But again, because we use malloc for the uids, I'd
suggest to use return-buffer and dealloc anyway.
I will make an appropriate patch and post it here.
Thanks,
Marcus
--
`Rhubarb is no Egyptian god.' Debian http://www.debian.org [EMAIL PROTECTED]
Marcus Brinkmann GNU http://www.gnu.org [EMAIL PROTECTED]
[EMAIL PROTECTED]
http://www.marcus-brinkmann.de
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