From: Elijah Newren <newren@xxxxxxxxx>
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 <newren@xxxxxxxxx>
---
merge-ort.c | 7 +++++++
merge-ort.h | 2 ++
2 files changed, 9 insertions(+)
diff --git a/merge-ort.c b/merge-ort.c
index bb47fa91a339..5d56b0f90128 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -52,6 +52,8 @@ enum merge_side {
MERGE_SIDE2 = 2
};
+static unsigned RESULT_INITIALIZED = 0x1abe11ed; /* unlikely accidental value */
+
struct traversal_callback_data {
unsigned long mask;
unsigned long dirmask;
@@ -3736,6 +3738,10 @@ static void merge_start(struct merge_options *opt, struct merge_result *result)
assert(opt->obuf.len == 0);
assert(opt->priv == NULL);
+ if (result->_properly_initialized != 0 &&
+ result->_properly_initialized != RESULT_INITIALIZED)
+ BUG("struct merge_result passed to merge_incore_*recursive() must be zeroed or filled with values from a previous run");
+ assert(!!result->priv == !!result->_properly_initialized);
if (result->priv) {
opt->priv = result->priv;
result->priv = NULL;
@@ -3895,6 +3901,7 @@ static void merge_ort_nonrecursive_internal(struct merge_options *opt,
result->clean &= strmap_empty(&opt->priv->conflicted);
if (!opt->priv->call_depth) {
result->priv = opt->priv;
+ result->_properly_initialized = RESULT_INITIALIZED;
opt->priv = NULL;
}
}
diff --git a/merge-ort.h b/merge-ort.h
index d53a0a339f33..c011864ffeb1 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;
};
/*
--
gitgitgadget
