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authorDavid Howells <dhowells@redhat.com>2007-02-09 09:30:37 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2007-02-23 16:24:27 -0800
commit76d21f587d66f8508f6448c7253e46ff1881bec9 (patch)
tree11d210b0a2fe75a633d2f86a04b616978edab82a
parent29b1320675ea8502790bb2dfd4098ab970ea6edb (diff)
Keys: Fix key serial number collision handling
Fix the key serial number collision avoidance code in key_alloc_serial(). This didn't use to be so much of a problem as the key serial numbers were allocated from a simple incremental counter, and it would have to go through two billion keys before it could possibly encounter a collision. However, now that random numbers are used instead, collisions are much more likely. This is fixed by finding a hole in the rbtree where the next unused serial number ought to be and using that by going almost back to the top of the insertion routine and redoing the insertion with the new serial number rather than trying to be clever and attempting to work out the insertion point pointer directly. This fixes kernel BZ #7727. Signed-off-by: David Howells <dhowells@redhat.com> Cc: Chuck Ebbert <cebbert@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--security/keys/key.c33
1 files changed, 14 insertions, 19 deletions
diff --git a/security/keys/key.c b/security/keys/key.c
index 80de8c3e9cc3..7b98397023d0 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -188,6 +188,7 @@ static inline void key_alloc_serial(struct key *key)
spin_lock(&key_serial_lock);
+attempt_insertion:
parent = NULL;
p = &key_serial_tree.rb_node;
@@ -202,39 +203,33 @@ static inline void key_alloc_serial(struct key *key)
else
goto serial_exists;
}
- goto insert_here;
+
+ /* we've found a suitable hole - arrange for this key to occupy it */
+ rb_link_node(&key->serial_node, parent, p);
+ rb_insert_color(&key->serial_node, &key_serial_tree);
+
+ spin_unlock(&key_serial_lock);
+ return;
/* we found a key with the proposed serial number - walk the tree from
* that point looking for the next unused serial number */
serial_exists:
for (;;) {
key->serial++;
- if (key->serial < 2)
- key->serial = 2;
-
- if (!rb_parent(parent))
- p = &key_serial_tree.rb_node;
- else if (rb_parent(parent)->rb_left == parent)
- p = &(rb_parent(parent)->rb_left);
- else
- p = &(rb_parent(parent)->rb_right);
+ if (key->serial < 3) {
+ key->serial = 3;
+ goto attempt_insertion;
+ }
parent = rb_next(parent);
if (!parent)
- break;
+ goto attempt_insertion;
xkey = rb_entry(parent, struct key, serial_node);
if (key->serial < xkey->serial)
- goto insert_here;
+ goto attempt_insertion;
}
- /* we've found a suitable hole - arrange for this key to occupy it */
-insert_here:
- rb_link_node(&key->serial_node, parent, p);
- rb_insert_color(&key->serial_node, &key_serial_tree);
-
- spin_unlock(&key_serial_lock);
-
} /* end key_alloc_serial() */
/*****************************************************************************/