Previously, when promisor_remote_move_to_tail() is called for a
promisor_remote which is currently the final element in promisors, a
cycle is created in the promisors linked list. This cycle leads to a
double free later on in promisor_remote_clear() when the final element
of the promisors list is removed: promisors is set to promisors->next (a
no-op, as promisors->next == promisors); the previous value of promisors
is free()'d; then the new value of promisors (which is equal to the
previous value of promisors) is also free()'d. This double-free error
was unrecoverable for the user without removing the filter or re-cloning
the repo and hoping to miss this edge case.
Now, when promisor_remote_move_to_tail() would be a no-op, just do a
no-op. In cases of promisor_remote_move_to_tail() where r is not already
at the tail of the list, it works as before.
Helped-by: Jeff King <peff@xxxxxxxx>
Signed-off-by: Emily Shaffer <emilyshaffer@xxxxxxxxxx>
---
Since v3 missed a small comment change.
promisor-remote.c | 3 +++
t/t0410-partial-clone.sh | 13 +++++++++++++
2 files changed, 16 insertions(+)
diff --git a/promisor-remote.c b/promisor-remote.c
index 9bc296cdde..9bd5b79d59 100644
--- a/promisor-remote.c
+++ b/promisor-remote.c
@@ -89,6 +89,9 @@ static struct promisor_remote *promisor_remote_lookup(const char *remote_name,
static void promisor_remote_move_to_tail(struct promisor_remote *r,
struct promisor_remote *previous)
{
+ if (r->next == NULL)
+ return;
+
if (previous)
previous->next = r->next;
else
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index d4b7e535ea..5c676c71a5 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -429,6 +429,19 @@ test_expect_success 'rev-list dies for missing objects on cmd line' '
done
'
+test_expect_success 'single promisor remote can be re-initialized gracefully' '
+ # ensure one promisor is in the promisors list
+ rm -rf repo &&
+ test_create_repo repo &&
+ test_create_repo other &&
+ git -C repo remote add foo "file://$(pwd)/other" &&
+ git -C repo config remote.foo.promisor true &&
+ git -C repo config extensions.partialclone foo &&
+
+ # reinitialize the promisors list
+ git -C repo fetch --filter=blob:none foo
+'
+
test_expect_success 'gc repacks promisor objects separately from non-promisor objects' '
rm -rf repo &&
test_create_repo repo &&
--
2.23.0.444.g18eeb5a265-goog
