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Null pointer dereference?


From: Zubin Mevawalla
Subject: Null pointer dereference?
Date: Fri, 12 May 2017 11:45:53 -0400

I was curious if this was a real null pointer dereference issue, in
etags.c on line 2265?

`np_parent` is initialized to NULL on 2248. if `np` is not NULL and
`np->fdp == badfdp` then `np_parent->left` on line 2265 would result
in a null pointer dereference.

CodeAi, an automated repair tool being developed at Qbit logic,
suggested a condition tightening as a fix.

diff --git a/lib-src/etags.c b/lib-src/etags.c
index 015cbbe..1f50d06 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -2260,7 +2260,7 @@ invalidate_nodes (fdesc *badfdp, node **npp)
              np_parent = np;
              np = np->left;
            }
-         if (np)
+         if (np_parent && (np))
            {
              np_parent->left = np->left; /* detach subtree from the tree */
              np->left = NULL;            /* isolate it */

Could I submit this as a patch if it looks alright?

Thanks so much,

Zubin



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