[PATCH net] s390/ism: add release function for struct device

[PATCH net] s390/ism: add release function for struct device

[Alexandra Winter]

From: Julian Ruess <julianr@linux.ibm.com>

According to device_release() in /drivers/base/core.c,
a device without a release function is a broken device
and must be fixed.

The current code directly frees the device after calling device_add()
without waiting for other kernel parts to release their references.
Thus, a reference could still be held to a struct device,
e.g., by sysfs, leading to potential use-after-free
issues if a proper release function is not set.

Fixes: 8c81ba20349d ("net/smc: De-tangle ism and smc device initialization")
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Signed-off-by: Julian Ruess <julianr@linux.ibm.com>
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
---
 drivers/s390/net/ism_drv.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
index e36e3ea165d3..2f34761e6413 100644
--- a/drivers/s390/net/ism_drv.c
+++ b/drivers/s390/net/ism_drv.c
@@ -588,6 +588,15 @@ static int ism_dev_init(struct ism_dev *ism)
 	return ret;
 }
 
+static void ism_dev_release(struct device *dev)
+{
+	struct ism_dev *ism;
+
+	ism = container_of(dev, struct ism_dev, dev);
+
+	kfree(ism);
+}
+
 static int ism_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
 	struct ism_dev *ism;
@@ -601,6 +610,7 @@ static int ism_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	dev_set_drvdata(&pdev->dev, ism);
 	ism->pdev = pdev;
 	ism->dev.parent = &pdev->dev;
+	ism->dev.release = ism_dev_release;
 	device_initialize(&ism->dev);
 	dev_set_name(&ism->dev, dev_name(&pdev->dev));
 	ret = device_add(&ism->dev);
@@ -637,7 +647,7 @@ static int ism_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	device_del(&ism->dev);
 err_dev:
 	dev_set_drvdata(&pdev->dev, NULL);
-	kfree(ism);
+	put_device(&ism->dev);
 
 	return ret;
 }
@@ -682,7 +692,7 @@ static void ism_remove(struct pci_dev *pdev)
 	pci_disable_device(pdev);
 	device_del(&ism->dev);
 	dev_set_drvdata(&pdev->dev, NULL);
-	kfree(ism);
+	put_device(&ism->dev);
 }
 
 static struct pci_driver ism_driver = {
-- 
2.45.2

Re: [PATCH net] s390/ism: add release function for struct device

[Simon Horman]

On Fri, Feb 14, 2025 at 01:01:37PM +0100, Alexandra Winter wrote:
> From: Julian Ruess <julianr@linux.ibm.com>
> 
> According to device_release() in /drivers/base/core.c,
> a device without a release function is a broken device
> and must be fixed.
> 
> The current code directly frees the device after calling device_add()
> without waiting for other kernel parts to release their references.
> Thus, a reference could still be held to a struct device,
> e.g., by sysfs, leading to potential use-after-free
> issues if a proper release function is not set.
> 
> Fixes: 8c81ba20349d ("net/smc: De-tangle ism and smc device initialization")
> Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
> Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
> Signed-off-by: Julian Ruess <julianr@linux.ibm.com>
> Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net] s390/ism: add release function for struct device

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 14 Feb 2025 13:01:37 +0100 you wrote:
> From: Julian Ruess <julianr@linux.ibm.com>
> 
> According to device_release() in /drivers/base/core.c,
> a device without a release function is a broken device
> and must be fixed.
> 
> The current code directly frees the device after calling device_add()
> without waiting for other kernel parts to release their references.
> Thus, a reference could still be held to a struct device,
> e.g., by sysfs, leading to potential use-after-free
> issues if a proper release function is not set.
> 
> [...]

Here is the summary with links:
  - [net] s390/ism: add release function for struct device
    https://git.kernel.org/netdev/net/c/915e34d5ad35

You are awesome, thank you!
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