[PATCH 1/2] soundwire: stream: roll back failed master registration

["Baek Kyu, Kim" <pocj8ur4in@gmail.com>]

When slaves have already created a master runtime, a failed master port
allocation leaves earlier allocations on its port list. If the second of
two port allocations fails, a retry sees a nonempty list and succeeds with
only one port and without incrementing m_rt_count.

Allocate master ports on a temporary list and publish them only after all
allocations succeed. On configuration failure, release ports allocated by
this call, balance m_rt_count, and restore the previous channel count and
direction. Preserve an existing slave-first runtime and its slaves, while
freeing a runtime created by the failed call. This lets a retry register
the complete set of ports instead of reusing a partial registration.

Fixes: ac3bc88cc56e ("soundwire: stream: separate alloc and config within sdw_stream_add_xxx()")
Fixes: f3016b891c8c ("soundwire: stream: sdw_stream_add_ functions can be called multiple times")
Signed-off-by: Baek Kyu, Kim <pocj8ur4in@gmail.com>
---
Tested with ARM64 QEMU KUnit using the real SoundWire registration APIs
and synthetic slave capabilities. Register a slave with two ports, fail
the second master port allocation, then disable fault injection and retry.
Before the fix the retry succeeds with one port and m_rt_count == 0;
afterwards it succeeds with two ports and m_rt_count == 1. Configuration
failure and existing/new runtime cases were also checked with KASAN and
lockdep enabled. No physical SoundWire hardware was tested.

 drivers/soundwire/stream.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index f106a877d7b2..8e94dcaf3784 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -1107,17 +1107,24 @@ static void sdw_master_port_free(struct sdw_master_runtime *m_rt)
 static int sdw_master_port_alloc(struct sdw_master_runtime *m_rt,
 				 unsigned int num_ports)
 {
-	struct sdw_port_runtime *p_rt;
+	struct sdw_port_runtime *p_rt, *tmp;
+	LIST_HEAD(port_list);
 	int i;
 
-	/* Iterate for number of ports to perform initialization */
+	/* Publish the ports only after the entire allocation succeeds. */
 	for (i = 0; i < num_ports; i++) {
-		p_rt = sdw_port_alloc(&m_rt->port_list);
+		p_rt = sdw_port_alloc(&port_list);
 		if (!p_rt)
-			return -ENOMEM;
+			goto free_ports;
 	}
 
+	list_splice_tail_init(&port_list, &m_rt->port_list);
 	return 0;
+
+free_ports:
+	list_for_each_entry_safe(p_rt, tmp, &port_list, port_node)
+		sdw_port_free(p_rt);
+	return -ENOMEM;
 }
 
 static int sdw_master_port_config(struct sdw_master_runtime *m_rt,
@@ -2017,6 +2024,9 @@ int sdw_stream_add_master(struct sdw_bus *bus,
 {
 	struct sdw_master_runtime *m_rt;
 	bool alloc_master_rt = false;
+	bool alloc_master_ports = false;
+	unsigned int old_ch_count;
+	enum sdw_data_direction old_direction;
 	int ret;
 
 	mutex_lock(&bus->bus_lock);
@@ -2056,26 +2066,39 @@ int sdw_stream_add_master(struct sdw_bus *bus,
 		alloc_master_rt = true;
 	}
 
+	old_ch_count = m_rt->ch_count;
+	old_direction = m_rt->direction;
+
 	if (!sdw_master_port_allocated(m_rt)) {
 		ret = sdw_master_port_alloc(m_rt, num_ports);
 		if (ret)
 			goto alloc_error;
 
 		stream->m_rt_count++;
+		alloc_master_ports = true;
 	}
 
 	ret = sdw_master_rt_config(m_rt, stream_config);
 	if (ret < 0)
-		goto unlock;
+		goto config_error;
 
 	ret = sdw_config_stream(bus->dev, stream, stream_config, false);
 	if (ret)
-		goto unlock;
+		goto config_error;
 
 	ret = sdw_master_port_config(m_rt, port_config);
+	if (ret)
+		goto config_error;
 
 	goto unlock;
 
+config_error:
+	m_rt->ch_count = old_ch_count;
+	m_rt->direction = old_direction;
+	if (alloc_master_ports) {
+		sdw_master_port_free(m_rt);
+		stream->m_rt_count--;
+	}
 alloc_error:
 	/*
 	 * we only cleanup what was allocated in this routine