[PATCH 6/7] oss-fuzz: handle reftable iterator initialization failures

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

The reftable fuzzer introduced by adf45165e65b (oss-fuzz: add fuzzer for
parsing reftables, 2026-07-03) ignored failures from
`reftable_table_init_ref_iterator()` and
`reftable_table_init_log_iterator()`. Coverity reported that under
allocation failure, either constructor can return
`REFTABLE_OUT_OF_MEMORY_ERROR` without installing an ops table, allowing
a subsequent seek to dereference NULL.

Treat iterator initialization failure as a reason to skip the
corresponding seek and iteration while retaining safe destruction for an
uninitialized iterator.

Assisted-by: GPT-5.6 Luna
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 oss-fuzz/fuzz-reftable.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/oss-fuzz/fuzz-reftable.c b/oss-fuzz/fuzz-reftable.c
index c46eac2c6b..75b8ad0c3d 100644
--- a/oss-fuzz/fuzz-reftable.c
+++ b/oss-fuzz/fuzz-reftable.c
@@ -33,10 +33,11 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 		struct reftable_ref_record ref = { 0 };
 		struct reftable_iterator it = { 0 };
 
-		reftable_table_init_ref_iterator(table, &it);
-		if (!reftable_iterator_seek_ref(&it, ""))
-			while (!reftable_iterator_next_ref(&it, &ref))
-				;
+		if (!reftable_table_init_ref_iterator(table, &it)) {
+			if (!reftable_iterator_seek_ref(&it, ""))
+				while (!reftable_iterator_next_ref(&it, &ref))
+					;
+		}
 
 		reftable_ref_record_release(&ref);
 		reftable_iterator_destroy(&it);
@@ -46,10 +47,11 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 		struct reftable_log_record log = { 0 };
 		struct reftable_iterator it = { 0 };
 
-		reftable_table_init_log_iterator(table, &it);
-		if (!reftable_iterator_seek_log(&it, ""))
-			while (!reftable_iterator_next_log(&it, &log))
-				;
+		if (!reftable_table_init_log_iterator(table, &it)) {
+			if (!reftable_iterator_seek_log(&it, ""))
+				while (!reftable_iterator_next_log(&it, &log))
+					;
+		}
 
 		reftable_log_record_release(&log);
 		reftable_iterator_destroy(&it);
-- 
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