BUG/MEDIUM: ebtree: Invalid read when looking for dup entry
The first item inserted into an ebtree will be inserted directly below
the root, which is a simple struct eb_root which only holds two branch
pointers (left and right).
If we try to find a duplicated entry to this first leaf through a
ebmb_next_dup, our leaf_p pointer will point to the eb_root instead of a
complete eb_node so we cannot look for the bit part of our leaf_p since
it would try to cast our eb_root into an eb_node and perform an out of
bounds access when reading "eb_root_to_node(eb_untag(t,EB_LEFT)))->bit".
This bug was found by address sanitizer running on a CRL hot update VTC
test.
Note that the bug has been there since the import of the eb_next_dup()
and eb_prev_dup() function in 1.5-dev19 by commit 2b5702030 ("MINOR:
ebtree: add new eb_next_dup/eb_prev_dup() functions to visit duplicates").
It can be backported to all stable branches.
(cherry picked from commit 2608e348bec8a533225424fad06760ce6e19f167)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/include/import/ebtree.h b/include/import/ebtree.h
index 85ea31d..36fcef5 100644
--- a/include/import/ebtree.h
+++ b/include/import/ebtree.h
@@ -615,12 +615,16 @@
t = (eb_root_to_node(eb_untag(t, EB_RGHT)))->node_p;
}
- /* Note that <t> cannot be NULL at this stage */
+ /* Note that <t> cannot be NULL at this stage. If our leaf is directly
+ * under the root, we must not try to cast the leaf_p into a eb_node*
+ * since it is a pointer to an eb_root.
+ */
+ if (eb_clrtag((eb_untag(t, EB_LEFT))->b[EB_RGHT]) == NULL)
+ return NULL;
+
if ((eb_root_to_node(eb_untag(t, EB_LEFT)))->bit >= 0)
return NULL;
t = (eb_untag(t, EB_LEFT))->b[EB_RGHT];
- if (eb_clrtag(t) == NULL)
- return NULL;
return eb_walk_down(t, EB_LEFT);
}