From f8763a02a1620844ed7326ea88ea8181e8b58aad Mon Sep 17 00:00:00 2001
From: Robert Baldyga <robert.baldyga@unvertical.com>
Date: Mon, 6 Jul 2026 15:43:50 +0200
Subject: [PATCH] generator: Protect against invalid values

__builtin_clz() produces undefined behavior for argument equal 0.
Implement proper handing of such a case.

Signed-off-by: Robert Baldyga <robert.baldyga@unvertical.com>
---
 src/ocf_lru.c               |  5 ++++-
 src/utils/utils_generator.c | 24 ++++++++++++++++++++----
 src/utils/utils_generator.h |  3 ++-
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/src/ocf_lru.c b/src/ocf_lru.c
index 7a0d959e4..af35aa2a8 100644
--- a/src/ocf_lru.c
+++ b/src/ocf_lru.c
@@ -1031,6 +1031,7 @@ static int ocf_lru_populate_handle(ocf_parallelize_t parallelize,
 	uint32_t partial_chunk_lines = 0;
 	uint32_t num_chunks, chunk_idx, chunk_lines;
 	uint32_t ci, j;
+	int result;
 
 	/* Check if this shard has a partial last chunk */
 	if (remainder > (uint32_t)shard_id * OCF_LRU_CHUNK_SIZE) {
@@ -1044,7 +1045,9 @@ static int ocf_lru_populate_handle(ocf_parallelize_t parallelize,
 	if (num_chunks == 0)
 		return 0;
 
-	ocf_generator_bisect_init(&generator, num_chunks, 0);
+	result = ocf_generator_bisect_init(&generator, num_chunks, 0);
+	if (result)
+		return result;
 
 	list = ocf_lru_get_list(&cache->free, shard_id, true);
 
diff --git a/src/utils/utils_generator.c b/src/utils/utils_generator.c
index 47ab7e653..e04c80291 100644
--- a/src/utils/utils_generator.c
+++ b/src/utils/utils_generator.c
@@ -1,5 +1,6 @@
 /*
  * Copyright(c) 2022 Intel Corporation
+ * Copyright(c) 2026 Unvertical
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
@@ -29,20 +30,32 @@ static inline uint32_t bitreverse32(register uint32_t x)
  *            returned by the generator is limit - 1)
  * @param[in] offset Offset at which generator should start
  *
- * @return Reversed value
+ * @return Zero when success, otherwise an error
  */
-void ocf_generator_bisect_init(
+int ocf_generator_bisect_init(
 		struct ocf_generator_bisect_state *generator,
 		uint32_t limit, uint32_t offset)
 {
 	unsigned clz;
 	uint32_t maplen;
 
-	clz = __builtin_clz(limit - 1);
-	maplen = 1 << (32 - clz);
+	if (limit == 0)
+		return -OCF_ERR_INVAL;
+
+	if (offset >= limit)
+		return -OCF_ERR_INVAL;
+
+	if (limit > 1) {
+		clz = __builtin_clz(limit - 1);
+		maplen = 1 << (32 - clz);
+	} else {
+		maplen = 1;
+	}
 
 	generator->curr = (uint64_t)offset * maplen / limit;
 	generator->limit = limit;
+
+	return 0;
 }
 
 /**
@@ -180,6 +193,9 @@ uint32_t ocf_generator_bisect_next(
 	uint32_t maplen;
 	uint32_t value;
 
+	if (generator->limit == 1)
+		return 0;
+
 	clz = __builtin_clz(generator->limit - 1);
 	maplen = 1 << (32 - clz);
 
diff --git a/src/utils/utils_generator.h b/src/utils/utils_generator.h
index 068602d0b..df8cb1ba1 100644
--- a/src/utils/utils_generator.h
+++ b/src/utils/utils_generator.h
@@ -1,5 +1,6 @@
 /*
  * Copyright(c) 2022 Intel Corporation
+ * Copyright(c) 2026 Unvertical
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
@@ -13,7 +14,7 @@ struct ocf_generator_bisect_state {
 	uint32_t limit;
 };
 
-void ocf_generator_bisect_init(
+int ocf_generator_bisect_init(
 		struct ocf_generator_bisect_state *generator,
 		uint32_t limit, uint32_t offset);