linux-kernel - [PATCH] assoc_array: don't call compare

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Message-Id: <1456157620-20819-1-git-send-email-jmarchan@redhat.com>
Date:	Mon, 22 Feb 2016 17:13:40 +0100
From:	"Jerome Marchand" <jmarchan@...hat.com>
To:	David Howells <dhowells@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] assoc_array: don't call compare_object() on a node

In assoc_array_insert_into_terminal_node(), we call the
compare_object() method on all empty slots, even when they're not
leaves, passing a pointer to an unexpected structure to
compare_object(). Currently it causes an out-of-bound read access in
keyring_compare_object detected by KASan. The issue is easily
reproduced with keyutils testsuite.
Only call compare_object() when the slot is a leave.

Signed-off-by: Jerome Marchand <jmarchan@...hat.com>
---
 lib/assoc_array.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index 03dd576..59fd7c0 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -524,7 +524,9 @@ static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
 			free_slot = i;
 			continue;
 		}
-		if (ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) {
+		if (assoc_array_ptr_is_leaf(ptr) &&
+		    ops->compare_object(assoc_array_ptr_to_leaf(ptr),
+					index_key)) {
 			pr_devel("replace in slot %d\n", i);
 			edit->leaf_p = &node->slots[i];
 			edit->dead_leaf = node->slots[i];
-- 
2.5.0