[PATCH v4 2/6] firmware_loader: Move module refcounts to allow unloading

[Dionna Glaze <dionnaglaze@google.com>]

If a kernel module registers a firmware upload API ops set, then it's
unable to be moved due to effectively a cyclic reference that the module
depends on the upload which depends on the module.

Instead, only require the try_module_get when an upload is requested to
disallow unloading a module only while the upload is in progress.

Fixes: 97730bbb242c ("firmware_loader: Add firmware-upload support")

CC: Sean Christopherson <seanjc@google.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: Borislav Petkov <bp@alien8.de>
CC: Dave Hansen <dave.hansen@linux.intel.com>
CC: Ashish Kalra <ashish.kalra@amd.com>
CC: Tom Lendacky <thomas.lendacky@amd.com>
CC: John Allen <john.allen@amd.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: "David S. Miller" <davem@davemloft.net>
CC: Michael Roth <michael.roth@amd.com>
CC: Luis Chamberlain <mcgrof@kernel.org>
CC: Russ Weight <russ.weight@linux.dev>
CC: Danilo Krummrich <dakr@redhat.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: "Rafael J. Wysocki" <rafael@kernel.org>
CC: Tianfei zhang <tianfei.zhang@intel.com>
CC: Alexey Kardashevskiy <aik@amd.com>

Tested-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Russ Weight <russ.weight@linux.dev>
Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
---
 drivers/base/firmware_loader/sysfs_upload.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/base/firmware_loader/sysfs_upload.c b/drivers/base/firmware_loader/sysfs_upload.c
index 829270067d163..7d9c6aef7720a 100644
--- a/drivers/base/firmware_loader/sysfs_upload.c
+++ b/drivers/base/firmware_loader/sysfs_upload.c
@@ -204,6 +204,7 @@ static void fw_upload_main(struct work_struct *work)
 		fwlp->ops->cleanup(fwl);
 
 putdev_exit:
+	module_put(fwlp->module);
 	put_device(fw_dev->parent);
 
 	/*
@@ -239,6 +240,9 @@ int fw_upload_start(struct fw_sysfs *fw_sysfs)
 	}
 
 	fwlp = fw_sysfs->fw_upload_priv;
+	if (!try_module_get(fwlp->module)) /* released in fw_upload_main */
+		return -EFAULT;
+
 	mutex_lock(&fwlp->lock);
 
 	/* Do not interfere with an on-going fw_upload */
@@ -310,13 +314,10 @@ firmware_upload_register(struct module *module, struct device *parent,
 		return ERR_PTR(-EINVAL);
 	}
 
-	if (!try_module_get(module))
-		return ERR_PTR(-EFAULT);
-
 	fw_upload = kzalloc(sizeof(*fw_upload), GFP_KERNEL);
 	if (!fw_upload) {
 		ret = -ENOMEM;
-		goto exit_module_put;
+		goto exit_err;
 	}
 
 	fw_upload_priv = kzalloc(sizeof(*fw_upload_priv), GFP_KERNEL);
@@ -358,7 +359,7 @@ firmware_upload_register(struct module *module, struct device *parent,
 	if (ret) {
 		dev_err(fw_dev, "%s: device_register failed\n", __func__);
 		put_device(fw_dev);
-		goto exit_module_put;
+		goto exit_err;
 	}
 
 	return fw_upload;
@@ -372,8 +373,7 @@ firmware_upload_register(struct module *module, struct device *parent,
 free_fw_upload:
 	kfree(fw_upload);
 
-exit_module_put:
-	module_put(module);
+exit_err:
 
 	return ERR_PTR(ret);
 }
@@ -387,7 +387,6 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
 {
 	struct fw_sysfs *fw_sysfs = fw_upload->priv;
 	struct fw_upload_priv *fw_upload_priv = fw_sysfs->fw_upload_priv;
-	struct module *module = fw_upload_priv->module;
 
 	mutex_lock(&fw_upload_priv->lock);
 	if (fw_upload_priv->progress == FW_UPLOAD_PROG_IDLE) {
@@ -403,6 +402,5 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
 
 unregister:
 	device_unregister(&fw_sysfs->dev);
-	module_put(module);
 }
 EXPORT_SYMBOL_GPL(firmware_upload_unregister);
-- 
2.47.0.199.ga7371fff76-goog