The leak is detected by the kernel memory leak detector (`kmemleak`)
following a `cxl create-region` failure:

 cxl_acpi ACPI0017:00: decoder0.0: created region2
 cxl region2: HPA allocation error (-34) for size:0x0000000100000000 in CXL Window 0 [mem 0xa90000000-0x1a8fffffff flags 0x200]
 kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

    __kmalloc_cache_noprof+0x28c/0x350
    get_free_mem_region+0x45/0x380
    alloc_free_mem_region+0x1d/0x30
    size_store+0x180/0x290 [cxl_core]
    kernfs_fop_write_iter+0x13f/0x1e0
    vfs_write+0x37c/0x540
    ksys_write+0x68/0xe0
    do_syscall_64+0x6e/0x190
    entry_SYSCALL_64_after_hwframe+0x76/0x7e

Fixes: 14b80582c43e ("resource: Introduce alloc_free_mem_region()")
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
---
 kernel/resource.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/resource.c b/kernel/resource.c
index 12004452d999..aa0b1da143eb 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -2000,6 +2000,8 @@ get_free_mem_region(struct device *dev, struct resource *base,
 		devres_free(dr);
 	} else if (dev)
 		devm_release_action(dev, remove_free_mem_region, res);
+	else
+		free_resource(res);
 
 	return ERR_PTR(-ERANGE);
 }
-- 
2.47.0

Li Zhijian wrote:
> The leak is detected by the kernel memory leak detector (`kmemleak`)
> following a `cxl create-region` failure:
> 
>  cxl_acpi ACPI0017:00: decoder0.0: created region2
>  cxl region2: HPA allocation error (-34) for size:0x0000000100000000 in CXL Window 0 [mem 0xa90000000-0x1a8fffffff flags 0x200]
>  kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
> 
>     __kmalloc_cache_noprof+0x28c/0x350
>     get_free_mem_region+0x45/0x380
>     alloc_free_mem_region+0x1d/0x30
>     size_store+0x180/0x290 [cxl_core]
>     kernfs_fop_write_iter+0x13f/0x1e0
>     vfs_write+0x37c/0x540
>     ksys_write+0x68/0xe0
>     do_syscall_64+0x6e/0x190
>     entry_SYSCALL_64_after_hwframe+0x76/0x7e
> 
> Fixes: 14b80582c43e ("resource: Introduce alloc_free_mem_region()")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> ---
>  kernel/resource.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 12004452d999..aa0b1da143eb 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -2000,6 +2000,8 @@ get_free_mem_region(struct device *dev, struct resource *base,
>  		devres_free(dr);
>  	} else if (dev)
>  		devm_release_action(dev, remove_free_mem_region, res);
> +	else
> +		free_resource(res);

This looks deceptively correct, but if the __insert_resource() call
succeeded above then this needs to optionally be paired with
remove_resource().

I think this function needs a rethink because mixing the devres, devm,
and alloc_resource() failure cases makes mistakes like this hard to see.

Here is a replacement proposal, only compile-tested:

-- >8 --
From a01a28304e547da1f6287eecf3aeb0ebc6f48e2b Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Tue, 4 Mar 2025 15:12:19 -0800
Subject: [PATCH] resource: Fix resource leak in get_free_mem_region()

Li reports a kmemleak detection in get_free_mem_region() error unwind
path:

  cxl region2: HPA allocation error (-34) for size:0x0000000100000000 in CXL Window 0 [mem 0xa90000000-0x1a8fffffff flags 0x200]
  kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

     __kmalloc_cache_noprof+0x28c/0x350
     get_free_mem_region+0x45/0x380
     alloc_free_mem_region+0x1d/0x30
     size_store+0x180/0x290 [cxl_core]
     kernfs_fop_write_iter+0x13f/0x1e0
     vfs_write+0x37c/0x540
     ksys_write+0x68/0xe0
     do_syscall_64+0x6e/0x190
     entry_SYSCALL_64_after_hwframe+0x76/0x7e

It turns out it not only leaks memory, also fails to unwind changes to
the resource tree (@base, usually iomem_resource).

Fix this by consolidating the devres and devm paths into just devres,
and move those details to a wrapper function. So now
__get_free_mem_region() only needs to worry about alloc_resource()
unwinding, and the devres failure path is resolved before touching the
resource tree.

Fixes: 14b80582c43e ("resource: Introduce alloc_free_mem_region()")
Reported-by: Li Zhijian <lizhijian@fujitsu.com>
Closes: http://lore.kernel.org/20250304043415.610286-1-lizhijian@fujitsu.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/resource.c | 105 ++++++++++++++++++++++++++--------------------
 1 file changed, 60 insertions(+), 45 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 12004452d999..80d10714cb38 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -172,6 +172,8 @@ static void free_resource(struct resource *res)
 		kfree(res);
 }
 
+DEFINE_FREE(free_resource, struct resource *, if (_T) free_resource(_T))
+
 static struct resource *alloc_resource(gfp_t flags)
 {
 	return kzalloc(sizeof(struct resource), flags);
@@ -1631,17 +1633,29 @@ void devm_release_resource(struct device *dev, struct resource *new)
 }
 EXPORT_SYMBOL(devm_release_resource);
 
+/*
+ * The GFR_REQUEST_REGION case performs a request_region() to be paired
+ * with release_region(). The alloc_free_mem_region() path performs
+ * insert_resource() to be paired with {remove,free}_resource(). The
+ * @res member differentiates the 2 cases.
+ */
 struct region_devres {
 	struct resource *parent;
 	resource_size_t start;
 	resource_size_t n;
+	struct resource *res;
 };
 
 static void devm_region_release(struct device *dev, void *res)
 {
 	struct region_devres *this = res;
 
-	__release_region(this->parent, this->start, this->n);
+	if (!this->res) {
+		__release_region(this->parent, this->start, this->n);
+	} else {
+		remove_resource(this->res);
+		free_resource(this->res);
+	}
 }
 
 static int devm_region_match(struct device *dev, void *res, void *match_data)
@@ -1908,43 +1922,19 @@ static resource_size_t gfr_next(resource_size_t addr, resource_size_t size,
 	return addr + size;
 }
 
-static void remove_free_mem_region(void *_res)
-{
-	struct resource *res = _res;
-
-	if (res->parent)
-		remove_resource(res);
-	free_resource(res);
-}
-
 static struct resource *
-get_free_mem_region(struct device *dev, struct resource *base,
-		    resource_size_t size, const unsigned long align,
-		    const char *name, const unsigned long desc,
-		    const unsigned long flags)
+__get_free_mem_region(struct resource *base, resource_size_t size,
+		      const unsigned long align, const char *name,
+		      const unsigned long desc, const unsigned long flags)
 {
 	resource_size_t addr;
-	struct resource *res;
-	struct region_devres *dr = NULL;
 
 	size = ALIGN(size, align);
 
-	res = alloc_resource(GFP_KERNEL);
+	struct resource *res __free(free_resource) = alloc_resource(GFP_KERNEL);
 	if (!res)
 		return ERR_PTR(-ENOMEM);
 
-	if (dev && (flags & GFR_REQUEST_REGION)) {
-		dr = devres_alloc(devm_region_release,
-				sizeof(struct region_devres), GFP_KERNEL);
-		if (!dr) {
-			free_resource(res);
-			return ERR_PTR(-ENOMEM);
-		}
-	} else if (dev) {
-		if (devm_add_action_or_reset(dev, remove_free_mem_region, res))
-			return ERR_PTR(-ENOMEM);
-	}
-
 	write_lock(&resource_lock);
 	for (addr = gfr_start(base, size, align, flags);
 	     gfr_continue(base, addr, align, flags);
@@ -1958,17 +1948,9 @@ get_free_mem_region(struct device *dev, struct resource *base,
 						    size, name, 0))
 				break;
 
-			if (dev) {
-				dr->parent = &iomem_resource;
-				dr->start = addr;
-				dr->n = size;
-				devres_add(dev, dr);
-			}
-
 			res->desc = desc;
 			write_unlock(&resource_lock);
 
-
 			/*
 			 * A driver is claiming this region so revoke any
 			 * mappings.
@@ -1985,25 +1967,58 @@ get_free_mem_region(struct device *dev, struct resource *base,
 			 * Only succeed if the resource hosts an exclusive
 			 * range after the insert
 			 */
-			if (__insert_resource(base, res) || res->child)
+			if (__insert_resource(base, res))
+				break;
+			if (res->child) {
+				remove_resource(res);
 				break;
+			}
 
 			write_unlock(&resource_lock);
 		}
 
-		return res;
+		return no_free_ptr(res);
 	}
 	write_unlock(&resource_lock);
 
-	if (flags & GFR_REQUEST_REGION) {
-		free_resource(res);
-		devres_free(dr);
-	} else if (dev)
-		devm_release_action(dev, remove_free_mem_region, res);
-
 	return ERR_PTR(-ERANGE);
 }
 
+static struct resource *
+get_free_mem_region(struct device *dev, struct resource *base,
+		    resource_size_t size, const unsigned long align,
+		    const char *name, const unsigned long desc,
+		    const unsigned long flags)
+{
+
+	struct region_devres *dr __free(kfree) = NULL;
+	struct resource *res;
+
+	if (dev) {
+		dr = devres_alloc(devm_region_release,
+				  sizeof(struct region_devres), GFP_KERNEL);
+		if (!dr)
+			return ERR_PTR(-ENOMEM);
+	}
+
+	res = __get_free_mem_region(base, size, align, name, desc, flags);
+
+	if (IS_ERR(res) || !dr)
+		return res;
+
+	dr->parent = base;
+	dr->start = res->start;
+	dr->n = resource_size(res);
+
+	/* See 'struct region_devres' definition for details */
+	if ((flags & GFR_REQUEST_REGION) == 0)
+		dr->res = res;
+
+	devres_add(dev, no_free_ptr(dr));
+
+	return res;
+}
+
 /**
  * devm_request_free_mem_region - find free region for device private memory
  *
-- 
2.48.1

On Tue, Mar 04, 2025 at 12:34:15PM +0800, Li Zhijian wrote:
> The leak is detected by the kernel memory leak detector (`kmemleak`)
> following a `cxl create-region` failure:
> 
>  cxl_acpi ACPI0017:00: decoder0.0: created region2
>  cxl region2: HPA allocation error (-34) for size:0x0000000100000000 in CXL Window 0 [mem 0xa90000000-0x1a8fffffff flags 0x200]
>  kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
> 
>     __kmalloc_cache_noprof+0x28c/0x350
>     get_free_mem_region+0x45/0x380
>     alloc_free_mem_region+0x1d/0x30
>     size_store+0x180/0x290 [cxl_core]

The below lines have no importance to be present in the commit message.
Please read Submitting Patches documentation that justifies my comment.

>     kernfs_fop_write_iter+0x13f/0x1e0
>     vfs_write+0x37c/0x540
>     ksys_write+0x68/0xe0
>     do_syscall_64+0x6e/0x190
>     entry_SYSCALL_64_after_hwframe+0x76/0x7e

-- 
With Best Regards,
Andy Shevchenko

On Tue, Mar 04, 2025 at 12:34:15PM +0800, Li Zhijian wrote:
> The leak is detected by the kernel memory leak detector (`kmemleak`)
> following a `cxl create-region` failure:
> 
>  cxl_acpi ACPI0017:00: decoder0.0: created region2
>  cxl region2: HPA allocation error (-34) for size:0x0000000100000000 in CXL Window 0 [mem 0xa90000000-0x1a8fffffff flags 0x200]
>  kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
> 
>     __kmalloc_cache_noprof+0x28c/0x350
>     get_free_mem_region+0x45/0x380
>     alloc_free_mem_region+0x1d/0x30
>     size_store+0x180/0x290 [cxl_core]
>     kernfs_fop_write_iter+0x13f/0x1e0
>     vfs_write+0x37c/0x540
>     ksys_write+0x68/0xe0
>     do_syscall_64+0x6e/0x190
>     entry_SYSCALL_64_after_hwframe+0x76/0x7e
> 
> Fixes: 14b80582c43e ("resource: Introduce alloc_free_mem_region()")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> ---
>  kernel/resource.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 12004452d999..aa0b1da143eb 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -2000,6 +2000,8 @@ get_free_mem_region(struct device *dev, struct resource *base,
>  		devres_free(dr);
>  	} else if (dev)
>  		devm_release_action(dev, remove_free_mem_region, res);
> +	else
> +		free_resource(res);

It should use {} as per coding style:

	} else {
		free_resource(res);
	}

(probably should add that to the previous branch too).

On 04/03/2025 17:22, Mika Westerberg wrote:
> On Tue, Mar 04, 2025 at 12:34:15PM +0800, Li Zhijian wrote:
>> The leak is detected by the kernel memory leak detector (`kmemleak`)
>> following a `cxl create-region` failure:
>>
>>   cxl_acpi ACPI0017:00: decoder0.0: created region2
>>   cxl region2: HPA allocation error (-34) for size:0x0000000100000000 in CXL Window 0 [mem 0xa90000000-0x1a8fffffff flags 0x200]
>>   kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
>>
>>      __kmalloc_cache_noprof+0x28c/0x350
>>      get_free_mem_region+0x45/0x380
>>      alloc_free_mem_region+0x1d/0x30
>>      size_store+0x180/0x290 [cxl_core]
>>      kernfs_fop_write_iter+0x13f/0x1e0
>>      vfs_write+0x37c/0x540
>>      ksys_write+0x68/0xe0
>>      do_syscall_64+0x6e/0x190
>>      entry_SYSCALL_64_after_hwframe+0x76/0x7e
>>
>> Fixes: 14b80582c43e ("resource: Introduce alloc_free_mem_region()")
>> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
>> ---
>>   kernel/resource.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/resource.c b/kernel/resource.c
>> index 12004452d999..aa0b1da143eb 100644
>> --- a/kernel/resource.c
>> +++ b/kernel/resource.c
>> @@ -2000,6 +2000,8 @@ get_free_mem_region(struct device *dev, struct resource *base,
>>   		devres_free(dr);
>>   	} else if (dev)
>>   		devm_release_action(dev, remove_free_mem_region, res);
>> +	else
>> +		free_resource(res);
> 
> It should use {} as per coding style:


The script/checkpatch.pl is happy with both of these 2 styles in practice.

Thanks
Zhijian

> 
> 	} else {
> 		free_resource(res);
> 	}
> 
> (probably should add that to the previous branch too).

On Tue, Mar 04, 2025 at 09:44:38AM +0000, Zhijian Li (Fujitsu) wrote:
> 
> 
> On 04/03/2025 17:22, Mika Westerberg wrote:
> > On Tue, Mar 04, 2025 at 12:34:15PM +0800, Li Zhijian wrote:
> >> The leak is detected by the kernel memory leak detector (`kmemleak`)
> >> following a `cxl create-region` failure:
> >>
> >>   cxl_acpi ACPI0017:00: decoder0.0: created region2
> >>   cxl region2: HPA allocation error (-34) for size:0x0000000100000000 in CXL Window 0 [mem 0xa90000000-0x1a8fffffff flags 0x200]
> >>   kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
> >>
> >>      __kmalloc_cache_noprof+0x28c/0x350
> >>      get_free_mem_region+0x45/0x380
> >>      alloc_free_mem_region+0x1d/0x30
> >>      size_store+0x180/0x290 [cxl_core]
> >>      kernfs_fop_write_iter+0x13f/0x1e0
> >>      vfs_write+0x37c/0x540
> >>      ksys_write+0x68/0xe0
> >>      do_syscall_64+0x6e/0x190
> >>      entry_SYSCALL_64_after_hwframe+0x76/0x7e
> >>
> >> Fixes: 14b80582c43e ("resource: Introduce alloc_free_mem_region()")
> >> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> >> ---
> >>   kernel/resource.c | 2 ++
> >>   1 file changed, 2 insertions(+)
> >>
> >> diff --git a/kernel/resource.c b/kernel/resource.c
> >> index 12004452d999..aa0b1da143eb 100644
> >> --- a/kernel/resource.c
> >> +++ b/kernel/resource.c
> >> @@ -2000,6 +2000,8 @@ get_free_mem_region(struct device *dev, struct resource *base,
> >>   		devres_free(dr);
> >>   	} else if (dev)
> >>   		devm_release_action(dev, remove_free_mem_region, res);
> >> +	else
> >> +		free_resource(res);
> > 
> > It should use {} as per coding style:
> 
> 
> The script/checkpatch.pl is happy with both of these 2 styles in practice.

It is but the coding style prefers then use {} around all branches, see:

https://docs.kernel.org/process/coding-style.html#placing-braces-and-spaces

	} else if (dev) {
		devm_release_action(dev, remove_free_mem_region, res);
	} else {
		free_resource(res);
	}