The VPP ancillary-client error path unregisters the CSI client before
destroying state->mutex. For I2P variants, the failure can occur before
mutex_init(), so cleanup destroys an uninitialized mutex.

Initialize the mutex immediately after allocating the driver state, before
creating any ancillary clients. This keeps every cleanup path matched with
a completed mutex initialization.

A QEMU x86_64 test using an i2c-stub bus instantiated an ADV7280 client
at address 0x21 and occupied its VPP ancillary address 0x42. This forced
i2c_new_ancillary_device() to return -EBUSY. An instrumentation oracle
observed an uninitialized mutex on the buggy kernel and an initialized
mutex on the fixed kernel. The failure was deliberately injected to
exercise the error path; no natural crash was observed.

Fixes: 851a54effbd8 ("[media] adv7180: Add I2P support")
Assisted-by: LLM Codex
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
---
 drivers/media/i2c/adv7180.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/i2c/adv7180.c b/drivers/media/i2c/adv7180.c
index a1c7f6822..8c2cf3f53 100644
--- a/drivers/media/i2c/adv7180.c
+++ b/drivers/media/i2c/adv7180.c
@@ -1454,6 +1454,7 @@ static int adv7180_probe(struct i2c_client *client)
 	if (state == NULL)
 		return -ENOMEM;
 
+	mutex_init(&state->mutex);
 	state->client = client;
 	state->field = V4L2_FIELD_ALTERNATE;
 	state->chip_info = i2c_get_match_data(client);
@@ -1497,7 +1498,6 @@ static int adv7180_probe(struct i2c_client *client)
 	}
 
 	state->irq = client->irq;
-	mutex_init(&state->mutex);
 	state->curr_norm = V4L2_STD_NTSC;
 
 	state->input = 0;
-- 
2.34.1