[PATCH v3 0/3] Convert manual kfree(dev) to put_device()

[PATCH v3 0/3] Convert manual kfree(dev) to put_device()

[Tarun Sahu]

Hello,

As per the kernel-doc guidelines, Devices that are tried to register
with device_register or to add using device_add, must use put_device
on their failure path (not kfree). This series contains 3 patches
for updating such instances. Same for kobject_init_and_add or
kobject_add, call kobject_put instead of kfree in case of error.

V3<-V1
1. Updated the commit msg of each patch to mention about the kernel-doc
   guidelines.

V2 <- V1
1. Removed patch [1] as it is part of another series [2] already.

[1]: https://lore.kernel.org/all/20260810162814.1398016-4-tarunsahu@google.com/
[2]: https://lore.kernel.org/all/20260724171945.2812749-5-shubhrajyoti.datta@amd.com/

Tarun Sahu (3):
  ARM: locomo: use put_device() on device_register() failure
  firmware/edd: use kobject_put() on edd_device_register() failure
  powerpc/ps3: use put_device() on device_register() failure in
    ps3_system_bus_device_register

 arch/arm/common/locomo.c                 | 13 ++--
 arch/powerpc/platforms/ps3/device-init.c | 83 ++++++++++++++----------
 arch/powerpc/platforms/ps3/system-bus.c  |  2 +
 drivers/firmware/edd.c                   |  2 +-
 4 files changed, 59 insertions(+), 41 deletions(-)


base-commit: ddca0cd800962b4121e5f2633005167bb6216175
-- 
2.55.0.691.gc56d675ccc-goog

[PATCH v3 1/3] ARM: locomo: use put_device() on device_register() failure

[Tarun Sahu]

As per device_register() function kernel documentation says "even
when device_register return error always use put_device() instead
of kfree()"

Fix such instance in locomo driver by replacing direct kfree(dev)
with put_device(&dev->dev) when device_register() returns an error.

Signed-off-by: Tarun Sahu <tarunsahu@google.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 arch/arm/common/locomo.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/arm/common/locomo.c b/arch/arm/common/locomo.c
index 55e360452828..0f6689d343b0 100644
--- a/arch/arm/common/locomo.c
+++ b/arch/arm/common/locomo.c
@@ -223,10 +223,8 @@ locomo_init_one_child(struct locomo *lchip, struct locomo_dev_info *info)
 	int ret;
 
 	dev = kzalloc_obj(struct locomo_dev);
-	if (!dev) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	if (!dev)
+		return -ENOMEM;
 
 	/*
 	 * If the parent device has a DMA mask associated with it,
@@ -255,10 +253,11 @@ locomo_init_one_child(struct locomo *lchip, struct locomo_dev_info *info)
 
 	ret = device_register(&dev->dev);
 	if (ret) {
- out:
-		kfree(dev);
+		put_device(&dev->dev);
+		return ret;
 	}
-	return ret;
+
+	return 0;
 }
 
 #ifdef CONFIG_PM
-- 
2.55.0.691.gc56d675ccc-goog

[PATCH v3 2/3] firmware/edd: use kobject_put() on edd_device_register() failure

[Tarun Sahu]

As per koject_init_and_add() function kernel document, even if this
function returns error kobject_put must be used instead of kfree.

When edd_device_register() fails after initializing the kobject with
kobject_init_and_add(), calling kfree(edev) directly bypasses the
kobject release callback (edd_release) and leaks the allocated kobject
resources.

Fix this by replacing direct kfree(edev) with kobject_put(&edev->kobj) on
registration failure.

Signed-off-by: Tarun Sahu <tarunsahu@google.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 drivers/firmware/edd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
index f980c5b56858..763e7b16d517 100644
--- a/drivers/firmware/edd.c
+++ b/drivers/firmware/edd.c
@@ -748,7 +748,7 @@ edd_init(void)
 
 		rc = edd_device_register(edev, i);
 		if (rc) {
-			kfree(edev);
+			kobject_put(&edev->kobj);
 			goto out;
 		}
 		edd_devices[i] = edev;
-- 
2.55.0.691.gc56d675ccc-goog

[PATCH v3 3/3] powerpc/ps3: use put_device() on device_register() failure in ps3_system_bus_device_register

[Tarun Sahu]

As per the kernel documentation of device_register() function, it is
important to call put_device even if device_register returns an error.

To follow this guidelines and properly release the resources after
device_register() failure, call put_device() instead of kfree()

Also there are in-function-defined struct layout which make struct device
(core) to be child of layout-child's member (layout.dev.core). Also
definition of struct layout is not unique across functions in the driver.
To be able to free struct layout's dynamic allocation via put_device we
need to make sure that the core's release function must call the free
on parent of core and the parent must be at the location 0 of the struct
layout which will inherently free struct layout. This is to not
complicate the code and keep it as it currently implemented. To check
the location of parent at 0 of struct layout, I have added BUILD_BUG_ON.

Signed-off-by: Tarun Sahu <tarunsahu@google.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 arch/powerpc/platforms/ps3/device-init.c | 83 ++++++++++++++----------
 arch/powerpc/platforms/ps3/system-bus.c  |  2 +
 2 files changed, 52 insertions(+), 33 deletions(-)

diff --git a/arch/powerpc/platforms/ps3/device-init.c b/arch/powerpc/platforms/ps3/device-init.c
index 9109c218a060..8d0c77db1764 100644
--- a/arch/powerpc/platforms/ps3/device-init.c
+++ b/arch/powerpc/platforms/ps3/device-init.c
@@ -90,14 +90,12 @@ static int __init ps3_register_lpm_devices(void)
 	if (result) {
 		pr_debug("%s:%d ps3_system_bus_device_register failed\n",
 			__func__, __LINE__);
-		goto fail_register;
+		return result;
 	}
 
 	pr_debug(" <- %s:%d\n", __func__, __LINE__);
 	return 0;
 
-
-fail_register:
 fail_rights:
 fail_read_repo:
 	kfree(dev);
@@ -121,6 +119,12 @@ static int __init ps3_setup_gelic_device(
 		struct ps3_dma_region d_region;
 	} *p;
 
+	/*
+	 * ps3_system_bus_release_device() calls kfree(&p->dev).
+	 * dev must be at offset 0 so kfree() frees outer p.
+	 */
+	BUILD_BUG_ON(offsetof(struct layout, dev) != 0);
+
 	pr_debug(" -> %s:%d\n", __func__, __LINE__);
 
 	BUG_ON(repo->bus_type != PS3_BUS_TYPE_SB);
@@ -164,13 +168,12 @@ static int __init ps3_setup_gelic_device(
 	if (result) {
 		pr_debug("%s:%d ps3_system_bus_device_register failed\n",
 			__func__, __LINE__);
-		goto fail_device_register;
+		return result;
 	}
 
 	pr_debug(" <- %s:%d\n", __func__, __LINE__);
 	return result;
 
-fail_device_register:
 fail_dma_init:
 fail_find_interrupt:
 	kfree(p);
@@ -192,6 +195,12 @@ static int __init ps3_setup_uhc_device(
 	u64 bus_addr;
 	u64 len;
 
+	/*
+	 * ps3_system_bus_release_device() calls kfree(&p->dev).
+	 * dev must be at offset 0 so kfree() frees outer p.
+	 */
+	BUILD_BUG_ON(offsetof(struct layout, dev) != 0);
+
 	pr_debug(" -> %s:%d\n", __func__, __LINE__);
 
 	BUG_ON(repo->bus_type != PS3_BUS_TYPE_SB);
@@ -252,13 +261,12 @@ static int __init ps3_setup_uhc_device(
 	if (result) {
 		pr_debug("%s:%d ps3_system_bus_device_register failed\n",
 			__func__, __LINE__);
-		goto fail_device_register;
+		return result;
 	}
 
 	pr_debug(" <- %s:%d\n", __func__, __LINE__);
 	return result;
 
-fail_device_register:
 fail_mmio_init:
 fail_dma_init:
 fail_find_reg:
@@ -291,6 +299,12 @@ static int __init ps3_setup_vuart_device(enum ps3_match_id match_id,
 		struct ps3_system_bus_device dev;
 	} *p;
 
+	/*
+	 * ps3_system_bus_release_device() calls kfree(&p->dev).
+	 * dev must be at offset 0 so kfree() frees outer p.
+	 */
+	BUILD_BUG_ON(offsetof(struct layout, dev) != 0);
+
 	pr_debug(" -> %s:%d: match_id %u, port %u\n", __func__, __LINE__,
 		match_id, port_number);
 
@@ -308,15 +322,10 @@ static int __init ps3_setup_vuart_device(enum ps3_match_id match_id,
 	if (result) {
 		pr_debug("%s:%d ps3_system_bus_device_register failed\n",
 			__func__, __LINE__);
-		goto fail_device_register;
+		return result;
 	}
 	pr_debug(" <- %s:%d\n", __func__, __LINE__);
 	return 0;
-
-fail_device_register:
-	kfree(p);
-	pr_debug(" <- %s:%d fail\n", __func__, __LINE__);
-	return result;
 }
 
 static int ps3_setup_storage_dev(const struct ps3_repository_device *repo,
@@ -327,6 +336,12 @@ static int ps3_setup_storage_dev(const struct ps3_repository_device *repo,
 	u64 port, blk_size, num_blocks;
 	unsigned int num_regions, i;
 
+	/*
+	 * ps3_system_bus_release_device() calls kfree(&p->sbd).
+	 * sbd must be at offset 0 so kfree() frees outer p.
+	 */
+	BUILD_BUG_ON(offsetof(struct ps3_storage_device, sbd) != 0);
+
 	pr_debug(" -> %s:%u: match_id %u\n", __func__, __LINE__, match_id);
 
 	result = ps3_repository_read_stor_dev_info(repo->bus_index,
@@ -395,13 +410,12 @@ static int ps3_setup_storage_dev(const struct ps3_repository_device *repo,
 	if (result) {
 		pr_debug("%s:%u ps3_system_bus_device_register failed\n",
 			 __func__, __LINE__);
-		goto fail_device_register;
+		return result;
 	}
 
 	pr_debug(" <- %s:%u\n", __func__, __LINE__);
 	return 0;
 
-fail_device_register:
 fail_read_region:
 fail_find_interrupt:
 	kfree(p);
@@ -445,6 +459,12 @@ static int __init ps3_register_sound_devices(void)
 		struct ps3_mmio_region m_region;
 	} *p;
 
+	/*
+	 * ps3_system_bus_release_device() calls kfree(&p->dev).
+	 * dev must be at offset 0 so kfree() frees outer p.
+	 */
+	BUILD_BUG_ON(offsetof(struct layout, dev) != 0);
+
 	pr_debug(" -> %s:%d\n", __func__, __LINE__);
 
 	p = kzalloc_obj(*p);
@@ -461,15 +481,10 @@ static int __init ps3_register_sound_devices(void)
 	if (result) {
 		pr_debug("%s:%d ps3_system_bus_device_register failed\n",
 			__func__, __LINE__);
-		goto fail_device_register;
+		return result;
 	}
 	pr_debug(" <- %s:%d\n", __func__, __LINE__);
 	return 0;
-
-fail_device_register:
-	kfree(p);
-	pr_debug(" <- %s:%d failed\n", __func__, __LINE__);
-	return result;
 }
 
 static int __init ps3_register_graphics_devices(void)
@@ -479,6 +494,12 @@ static int __init ps3_register_graphics_devices(void)
 		struct ps3_system_bus_device dev;
 	} *p;
 
+	/*
+	 * ps3_system_bus_release_device() calls kfree(&p->dev).
+	 * dev must be at offset 0 so kfree() frees outer p.
+	 */
+	BUILD_BUG_ON(offsetof(struct layout, dev) != 0);
+
 	pr_debug(" -> %s:%d\n", __func__, __LINE__);
 
 	p = kzalloc_obj(struct layout);
@@ -495,16 +516,11 @@ static int __init ps3_register_graphics_devices(void)
 	if (result) {
 		pr_debug("%s:%d ps3_system_bus_device_register failed\n",
 			__func__, __LINE__);
-		goto fail_device_register;
+		return result;
 	}
 
 	pr_debug(" <- %s:%d\n", __func__, __LINE__);
 	return 0;
-
-fail_device_register:
-	kfree(p);
-	pr_debug(" <- %s:%d failed\n", __func__, __LINE__);
-	return result;
 }
 
 static int __init ps3_register_ramdisk_device(void)
@@ -514,6 +530,12 @@ static int __init ps3_register_ramdisk_device(void)
 		struct ps3_system_bus_device dev;
 	} *p;
 
+	/*
+	 * ps3_system_bus_release_device() calls kfree(&p->dev).
+	 * dev must be at offset 0 so kfree() frees outer p.
+	 */
+	BUILD_BUG_ON(offsetof(struct layout, dev) != 0);
+
 	pr_debug(" -> %s:%d\n", __func__, __LINE__);
 
 	p = kzalloc_obj(struct layout);
@@ -530,16 +552,11 @@ static int __init ps3_register_ramdisk_device(void)
 	if (result) {
 		pr_debug("%s:%d ps3_system_bus_device_register failed\n",
 			__func__, __LINE__);
-		goto fail_device_register;
+		return result;
 	}
 
 	pr_debug(" <- %s:%d\n", __func__, __LINE__);
 	return 0;
-
-fail_device_register:
-	kfree(p);
-	pr_debug(" <- %s:%d failed\n", __func__, __LINE__);
-	return result;
 }
 
 /**
diff --git a/arch/powerpc/platforms/ps3/system-bus.c b/arch/powerpc/platforms/ps3/system-bus.c
index 0537a678a32f..0918c74d3e19 100644
--- a/arch/powerpc/platforms/ps3/system-bus.c
+++ b/arch/powerpc/platforms/ps3/system-bus.c
@@ -774,6 +774,8 @@ int ps3_system_bus_device_register(struct ps3_system_bus_device *dev)
 	pr_debug("%s:%d add %s\n", __func__, __LINE__, dev_name(&dev->core));
 
 	result = device_register(&dev->core);
+	if (result)
+		put_device(&dev->core);
 	return result;
 }
 
-- 
2.55.0.691.gc56d675ccc-goog

Re: [PATCH v3 2/3] firmware/edd: use kobject_put() on edd_device_register() failure

[Bjorn Helgaas]

On Fri, Aug 14, 2026 at 09:00:56PM +0000, Tarun Sahu wrote:
> As per koject_init_and_add() function kernel document, even if this
> function returns error kobject_put must be used instead of kfree.

Thanks for adding this specific pointer.  I wouldn't repost just for
these nits, and wait at least a few days before reposting for any
reason.  But if you do repost:

s/koject_init_and_add/kobject_init_and_add/

Might also add "()" after function names consistently (kobject_put and
kfree above, edd_release below).  Also applies to the other patches.

The current subject lines basically restate the C code; you might
consider more of a focus on the problem.  I ran this through gemini
and I think it did a decent job:

  firmware: edd: Fix kobject reference leak on registration failure

  Per kobject_init_and_add() kernel-doc, calling kfree() directly on
  error bypasses reference counting and skips the kobject's release
  callback, leaking the reference.

  Use kobject_put() instead of kfree() on registration failure to fix
  this.

> When edd_device_register() fails after initializing the kobject with
> kobject_init_and_add(), calling kfree(edev) directly bypasses the
> kobject release callback (edd_release) and leaks the allocated kobject
> resources.
> 
> Fix this by replacing direct kfree(edev) with kobject_put(&edev->kobj) on
> registration failure.
> 
> Signed-off-by: Tarun Sahu <tarunsahu@google.com>
> Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> ---
>  drivers/firmware/edd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
> index f980c5b56858..763e7b16d517 100644
> --- a/drivers/firmware/edd.c
> +++ b/drivers/firmware/edd.c
> @@ -748,7 +748,7 @@ edd_init(void)
>  
>  		rc = edd_device_register(edev, i);
>  		if (rc) {
> -			kfree(edev);
> +			kobject_put(&edev->kobj);
>  			goto out;
>  		}
>  		edd_devices[i] = edev;
> -- 
> 2.55.0.691.gc56d675ccc-goog
>