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 <[email protected]>
Tested-by: Stephen Gallagher <[email protected]>
---
security/keys/keyring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 3dd8445cd489..d46cbc5e335e 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -690,8 +690,8 @@ descend_to_node:
smp_read_barrier_depends();
ptr = ACCESS_ONCE(shortcut->next_node);
BUG_ON(!assoc_array_ptr_is_node(ptr));
- node = assoc_array_ptr_to_node(ptr);
}
+ node = assoc_array_ptr_to_node(ptr);
begin_node:
kdebug("begin_node");
--
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