KEYS: Fix searching of nested keyrings

If a keyring contains more than 16 keyrings (the capacity of a single node in
the associative array) then those keyrings are split over multiple nodes
arranged as a tree.

If search_nested_keyrings() is called to search the keyring then it will
attempt to manually walk over just the 0 branch of the associative array tree
where all the keyring links are stored.  This works provided the key is found
before the algorithm steps from one node containing keyrings to a child node
or if there are sufficiently few keyring links that the keyrings are all in
one node.

However, if the algorithm does need to step from a node to a child node, it
doesn't change the node pointer unless a shortcut also gets transited.  This
means that the algorithm will keep scanning the same node over and over again
without terminating and without returning.

To fix this, move the internal-pointer-to-node translation from inside the
shortcut transit handler so that it applies it to node arrival as well.

This can be tested by:

	r=`keyctl newring sandbox @s`
	for ((i=0; i<=16; i++)); do keyctl newring ring$i $r; done
	for ((i=0; i<=16; i++)); do keyctl add user a$i a %:ring$i; done
	for ((i=0; i<=16; i++)); do keyctl search $r user a$i; done
	for ((i=17; i<=20; i++)); do keyctl search $r user a$i; done

The searches should all complete successfully (or with an error for 17-20),
but instead one or more of them will hang.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Stephen Gallagher <sgallagh@redhat.com>
This commit is contained in:
David Howells 2013-12-02 11:24:19 +00:00
parent 23fd78d764
commit 9c5e45df21

View file

@ -690,8 +690,8 @@ static bool search_nested_keyrings(struct key *keyring,
smp_read_barrier_depends(); smp_read_barrier_depends();
ptr = ACCESS_ONCE(shortcut->next_node); ptr = ACCESS_ONCE(shortcut->next_node);
BUG_ON(!assoc_array_ptr_is_node(ptr)); BUG_ON(!assoc_array_ptr_is_node(ptr));
node = assoc_array_ptr_to_node(ptr);
} }
node = assoc_array_ptr_to_node(ptr);
begin_node: begin_node:
kdebug("begin_node"); kdebug("begin_node");