ubd: Use pointer-to-pointers for io_thread_req arrays

Having an unbounded array for irq_req_buffer and io_req_buffer doesn't
provide any bounds safety, and confuses the needed allocation type,
which is returning a pointer to pointers. Instead of the implicit cast,
switch the variable types.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Closes: https://lore.kernel.org/all/b04b6c13-7d0e-4a89-9e68-b572b6c686ac@roeck-us.net
Fixes: 69050f8 ("treewide: Replace kmalloc with kmalloc_obj for non-scalar types")
Acked-by: Richard Weinberger <richard@nod.at>
Link: https://patch.msgid.link/20260223214341.work.846-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

Author: kees

arch/um/drivers/ubd_kern.c

@@ -69,11 +69,11 @@ struct io_thread_req {
 };
 
 
-static struct io_thread_req * (*irq_req_buffer)[];
+static struct io_thread_req **irq_req_buffer;
 static struct io_thread_req *irq_remainder;
 static int irq_remainder_size;
 
-static struct io_thread_req * (*io_req_buffer)[];
+static struct io_thread_req **io_req_buffer;
 static struct io_thread_req *io_remainder;
 static int io_remainder_size;
 
@@ -398,7 +398,7 @@ static int thread_fd = -1;
 
 static int bulk_req_safe_read(
 	int fd,
-	struct io_thread_req * (*request_buffer)[],
+	struct io_thread_req **request_buffer,
 	struct io_thread_req **remainder,
 	int *remainder_size,
 	int max_recs
@@ -465,7 +465,7 @@ static irqreturn_t ubd_intr(int irq, void *dev)
 			&irq_remainder, &irq_remainder_size,
 			UBD_REQ_BUFFER_SIZE)) >= 0) {
 		for (i = 0; i < len / sizeof(struct io_thread_req *); i++)
-			ubd_end_request((*irq_req_buffer)[i]);
+			ubd_end_request(irq_req_buffer[i]);
 	}
 
 	if (len < 0 && len != -EAGAIN)
@@ -1512,7 +1512,7 @@ void *io_thread(void *arg)
 		}
 
 		for (count = 0; count < n/sizeof(struct io_thread_req *); count++) {
-			struct io_thread_req *req = (*io_req_buffer)[count];
+			struct io_thread_req *req = io_req_buffer[count];
 			int i;
 
 			io_count++;