From 19ceb486f8dd25fb5782724c454edb2f06f1ed71 Mon Sep 17 00:00:00 2001 From: Elijah Newren Date: Thu, 20 May 2021 06:09:37 +0000 Subject: merge-ort: avoid accidental API mis-use Previously, callers of the merge-ort API could have passed an uninitialized value for struct merge_result *result. However, we want to check result to see if it has cached renames from a previous merge that we can reuse; such values would be found behind result->priv. However, if result->priv is uninitialized, attempting to access behind it will give a segfault. So, we need result->priv to be NULL (which will be the case if the caller does a memset(&result, 0)), or be written by a previous call to the merge-ort machinery. Documenting this requirement may help, but despite being the person who introduced this requirement, I still missed it once and it did not fail in a very clear way and led to a long debugging session. Add a _properly_initialized field to merge_result; that value will be 0 if the caller zero'ed the merge_result, it will be set to a very specific value by a previous run by the merge-ort machinery, and if it's uninitialized it will most likely either be 0 or some value that does not match the specific one we'd expect allowing us to throw a much more meaningful error. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano --- merge-ort.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'merge-ort.h') diff --git a/merge-ort.h b/merge-ort.h index d53a0a339f..c011864ffe 100644 --- a/merge-ort.h +++ b/merge-ort.h @@ -29,6 +29,8 @@ struct merge_result { * !clean) and to print "CONFLICT" messages. Not for external use. */ void *priv; + /* Also private */ + unsigned _properly_initialized; }; /* -- cgit v1.2.3