Re: [PATCH] Keys: Add possessor permissions to keys

From: Andrew Morton (akpm_at_osdl.org)
Date: 09/21/05

  • Next message: Martin Mares: "Re: PCI Express or TG3 issue" 
    Date:	Wed, 21 Sep 2005 10:15:58 -0700
To: David Howells <dhowells@redhat.com>

    David Howells <dhowells@redhat.com> wrote:
    >
    >
    > The attached patch adds extra permission grants to keys for the possessor of a
    > key in addition to the owner, group and other permissions bits. This makes
    > SUID binaries easier to support without going as far as labelling keys and key
    > targets using the LSM facilities.
    >
    > This patch adds a second "pointer type" to key structures (struct key_ref *)
    > that can have the bottom bit of the address set to indicate the possession of
    > a key. This is propagated through searches from the keyring to the discovered
    > key. It has been made a separate type so that the compiler can spot attempts
    > to dereference a potentially incorrect pointer.

    The above bit needs to be captured in a code comment. Because:

    > ...
    > /*
    > + * key reference with possession flag handling
    > + */
    > +static inline struct key_ref *key_mkref(const struct key *key, unsigned long possession)
    > +{
    > + return (struct key_ref *) ((unsigned long) key | possession);
    > +}

    Is hair-raising and makes people want to come after you with a stick ;)

    (And an 80-col xterm)

    ugh, I see. `struct key_ref' doesn't actually exist anywhere. The code
    only ever deals with pointers to this non-existent structure and they are
    munged `struct key *'s.

    Did this _have_ to happen?

    > + }
    > + else if (key->uid == context->fsuid) {

    Documentation/CodingStyle?

    > + "%s;%d;%d;%08x;%s",
    > + key_deref(key)->type->name,
    > + key_deref(key)->uid,
    > + key_deref(key)->gid,
    > + key_deref(key)->perm,
    > + key_deref(key)->description ? key_deref(key)->description : ""
    > );

    This doesn't actually make things clear.

    > + if (PTR_ERR(key_ref) != -EAGAIN) {
    > + if (IS_ERR(key_ref))
    > + key = key_deref(key_ref);
    > + else
    > + key = ERR_PTR(PTR_ERR(key_ref));
    > + break;
    > + }
    > + }

    That's getting a bit intimate with how IS_ERR and PTR_ERR are implemented
    but I guess we're unlikely to change that.

    This all seems quite inappropriate to -rc2?
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