If visit_guest() fails, then it returns a null pointer; later on, free_tree() is called unconditionally on the variables, thus dereferencing null pointers. Thus guard the free_tree() invocations. --- diff/diff.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/diff/diff.c b/diff/diff.c index 5851a1c9c..1f1ab6933 100644 --- a/diff/diff.c +++ b/diff/diff.c @@ -389,8 +389,10 @@ main (int argc, char *argv[]) errors++; } - free_tree (tree1); - free_tree (tree2); + if (tree1) + free_tree (tree1); + if (tree2) + free_tree (tree2); free_drives (drvs); free_drives (drvs2); -- 2.13.6