[PATCH 6.12 271/337] of: reserved_mem: avoid post-init UAF when alloc_reserved_mem_array() fails

6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Wandun Chen <[email protected]>

commit e1686ca81dbf3edbde589b7daf312b45cbf76e03 upstream.

The global pointer 'reserved_mem' continues to reference the
reserved_mem_array which lives in __initdata if
alloc_reserved_mem_array() fails. of_reserved_mem_lookup() is
exported for post-init use, that would dereference freed memory
and trigger a use-after-free.

So reset reserved_mem_count to 0 when alloc_reserved_mem_array()
fails.

Fixes: 00c9a452a235 ("of: reserved_mem: Add code to dynamically allocate reserved_mem array")
Signed-off-by: Wandun Chen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Rob Herring (Arm) <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 drivers/of/of_reserved_mem.c |   28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -70,29 +70,32 @@ static int __init early_init_dt_alloc_re
  * the initial static array is copied over to this new array and
  * the new array is used from this point on.
  */
-static void __init alloc_reserved_mem_array(void)
+static int __init alloc_reserved_mem_array(void)
 {
 	struct reserved_mem *new_array;
 	size_t alloc_size, copy_size, memset_size;
+	int ret;
+
+	if (!total_reserved_mem_cnt)
+		return 0;
 
 	alloc_size = array_size(total_reserved_mem_cnt, sizeof(*new_array));
 	if (alloc_size == SIZE_MAX) {
-		pr_err("Failed to allocate memory for reserved_mem array with err: %d", -EOVERFLOW);
-		return;
+		ret = -EOVERFLOW;
+		goto fail;
 	}
 
 	new_array = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
 	if (!new_array) {
-		pr_err("Failed to allocate memory for reserved_mem array with err: %d", -ENOMEM);
-		return;
+		ret = -ENOMEM;
+		goto fail;
 	}
 
 	copy_size = array_size(reserved_mem_count, sizeof(*new_array));
 	if (copy_size == SIZE_MAX) {
 		memblock_free(new_array, alloc_size);
-		total_reserved_mem_cnt = MAX_RESERVED_REGIONS;
-		pr_err("Failed to allocate memory for reserved_mem array with err: %d", -EOVERFLOW);
-		return;
+		ret = -EOVERFLOW;
+		goto fail;
 	}
 
 	memset_size = alloc_size - copy_size;
@@ -101,6 +104,12 @@ static void __init alloc_reserved_mem_ar
 	memset(new_array + reserved_mem_count, 0, memset_size);
 
 	reserved_mem = new_array;
+	return 0;
+
+fail:
+	pr_err("Failed to allocate memory for reserved_mem array with err: %d", ret);
+	reserved_mem_count = 0;
+	return ret;
 }
 
 static void __init fdt_init_reserved_mem_node(struct reserved_mem *rmem);
@@ -246,7 +255,8 @@ void __init fdt_scan_reserved_mem_reg_no
 	}
 
 	/* Attempt dynamic allocation of a new reserved_mem array */
-	alloc_reserved_mem_array();
+	if (alloc_reserved_mem_array())
+		return;
 
 	if (__reserved_mem_check_root(node)) {
 		pr_err("Reserved memory: unsupported node format, ignoring\n");