netdev - [PATCH 1/3] s390/vmlogrdr: Remove function pointer cast

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Message-Id: <20240417-s390-drivers-fix-cast-function-type-v1-1-fd048c9903b0@kernel.org>
Date: Wed, 17 Apr 2024 11:24:35 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: akpm@...ux-foundation.org, arnd@...db.de, hca@...ux.ibm.com, 
 gor@...ux.ibm.com, agordeev@...ux.ibm.com
Cc: borntraeger@...ux.ibm.com, svens@...ux.ibm.com, wintera@...ux.ibm.com, 
 twinkler@...ux.ibm.com, linux-s390@...r.kernel.org, netdev@...r.kernel.org, 
 llvm@...ts.linux.dev, patches@...ts.linux.dev, 
 Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH 1/3] s390/vmlogrdr: Remove function pointer cast

Clang warns (or errors with CONFIG_WERROR) after enabling
-Wcast-function-type-strict by default:

  drivers/s390/char/vmlogrdr.c:746:18: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
    746 |                 dev->release = (void (*)(struct device *))kfree;
        |                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  1 error generated.

Add a standalone function to fix the warning properly, which addresses
the root of the warning that these casts are not safe for kCFI. The
comment is not really relevant after this change, so remove it.

Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/s390/char/vmlogrdr.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/s390/char/vmlogrdr.c b/drivers/s390/char/vmlogrdr.c
index d7e408c8d0b8..8f90f58b680a 100644
--- a/drivers/s390/char/vmlogrdr.c
+++ b/drivers/s390/char/vmlogrdr.c
@@ -722,6 +722,10 @@ static void vmlogrdr_unregister_driver(void)
 	iucv_unregister(&vmlogrdr_iucv_handler, 1);
 }
 
+static void vmlogrdr_free_dev(struct device *dev)
+{
+	kfree(dev);
+}
 
 static int vmlogrdr_register_device(struct vmlogrdr_priv_t *priv)
 {
@@ -736,14 +740,7 @@ static int vmlogrdr_register_device(struct vmlogrdr_priv_t *priv)
 		dev->driver = &vmlogrdr_driver;
 		dev->groups = vmlogrdr_attr_groups;
 		dev_set_drvdata(dev, priv);
-		/*
-		 * The release function could be called after the
-		 * module has been unloaded. It's _only_ task is to
-		 * free the struct. Therefore, we specify kfree()
-		 * directly here. (Probably a little bit obfuscating
-		 * but legitime ...).
-		 */
-		dev->release = (void (*)(struct device *))kfree;
+		dev->release = vmlogrdr_free_dev;
 	} else
 		return -ENOMEM;
 	ret = device_register(dev);

-- 
2.44.0