[PATCH net] platform/x86: intel_pmc_ipc: fix ACPI buffer memory leak

[PATCH net] platform/x86: intel_pmc_ipc: fix ACPI buffer memory leak

[yongxin.liu]

From: Yongxin Liu <yongxin.liu@windriver.com>

The intel_pmc_ipc() function uses ACPI_ALLOCATE_BUFFER to allocate memory
for the ACPI evaluation result but never frees it, causing a 192-byte
memory leak on each call.

This leak is triggered during network interface initialization when the
stmmac driver calls intel_mac_finish() -> intel_pmc_ipc().

  unreferenced object 0xffff96a848d6ea80 (size 192):
    comm "dhcpcd", pid 541, jiffies 4294684345
    hex dump (first 32 bytes):
      04 00 00 00 05 00 00 00 98 ea d6 48 a8 96 ff ff  ...........H....
      00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
    backtrace (crc b1564374):
      kmemleak_alloc+0x2d/0x40
      __kmalloc_noprof+0x2fa/0x730
      acpi_ut_initialize_buffer+0x83/0xc0
      acpi_evaluate_object+0x29a/0x2f0
      intel_pmc_ipc+0xfd/0x170
      intel_mac_finish+0x168/0x230
      stmmac_mac_finish+0x3d/0x50
      phylink_major_config+0x22b/0x5b0
      phylink_mac_initial_config.constprop.0+0xf1/0x1b0
      phylink_start+0x8e/0x210
      __stmmac_open+0x12c/0x2b0
      stmmac_open+0x23c/0x380
      __dev_open+0x11d/0x2c0
      __dev_change_flags+0x1d2/0x250
      netif_change_flags+0x2b/0x70
      dev_change_flags+0x40/0xb0

Add kfree() to properly release the allocated buffer.

Cc: stable@vger.kernel.org
Fixes: 7e2f7e25f6ff ("arch: x86: add IPC mailbox accessor function and add SoC register access")
Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
---
 include/linux/platform_data/x86/intel_pmc_ipc.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/platform_data/x86/intel_pmc_ipc.h b/include/linux/platform_data/x86/intel_pmc_ipc.h
index 1d34435b7001..2fd5e684ce26 100644
--- a/include/linux/platform_data/x86/intel_pmc_ipc.h
+++ b/include/linux/platform_data/x86/intel_pmc_ipc.h
@@ -89,6 +89,7 @@ static inline int intel_pmc_ipc(struct pmc_ipc_cmd *ipc_cmd, struct pmc_ipc_rbuf
 		return -EINVAL;
 	}
 
+	kfree (obj);
 	return 0;
 #else
 	return -ENODEV;
-- 
2.46.2

Re: [PATCH net] platform/x86: intel_pmc_ipc: fix ACPI buffer memory leak

[Ilpo Järvinen]

On Mon, 24 Nov 2025, yongxin.liu@windriver.com wrote:

> From: Yongxin Liu <yongxin.liu@windriver.com>
> 
> The intel_pmc_ipc() function uses ACPI_ALLOCATE_BUFFER to allocate memory
> for the ACPI evaluation result but never frees it, causing a 192-byte
> memory leak on each call.
> 
> This leak is triggered during network interface initialization when the
> stmmac driver calls intel_mac_finish() -> intel_pmc_ipc().
> 
>   unreferenced object 0xffff96a848d6ea80 (size 192):
>     comm "dhcpcd", pid 541, jiffies 4294684345
>     hex dump (first 32 bytes):
>       04 00 00 00 05 00 00 00 98 ea d6 48 a8 96 ff ff  ...........H....
>       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
>     backtrace (crc b1564374):
>       kmemleak_alloc+0x2d/0x40
>       __kmalloc_noprof+0x2fa/0x730
>       acpi_ut_initialize_buffer+0x83/0xc0
>       acpi_evaluate_object+0x29a/0x2f0
>       intel_pmc_ipc+0xfd/0x170
>       intel_mac_finish+0x168/0x230
>       stmmac_mac_finish+0x3d/0x50
>       phylink_major_config+0x22b/0x5b0
>       phylink_mac_initial_config.constprop.0+0xf1/0x1b0
>       phylink_start+0x8e/0x210
>       __stmmac_open+0x12c/0x2b0
>       stmmac_open+0x23c/0x380
>       __dev_open+0x11d/0x2c0
>       __dev_change_flags+0x1d2/0x250
>       netif_change_flags+0x2b/0x70
>       dev_change_flags+0x40/0xb0
> 
> Add kfree() to properly release the allocated buffer.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7e2f7e25f6ff ("arch: x86: add IPC mailbox accessor function and add SoC register access")
> Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
> ---
>  include/linux/platform_data/x86/intel_pmc_ipc.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/platform_data/x86/intel_pmc_ipc.h b/include/linux/platform_data/x86/intel_pmc_ipc.h
> index 1d34435b7001..2fd5e684ce26 100644
> --- a/include/linux/platform_data/x86/intel_pmc_ipc.h
> +++ b/include/linux/platform_data/x86/intel_pmc_ipc.h
> @@ -89,6 +89,7 @@ static inline int intel_pmc_ipc(struct pmc_ipc_cmd *ipc_cmd, struct pmc_ipc_rbuf
>  		return -EINVAL;
>  	}
>  
> +	kfree (obj);

Good catch but this fix doesn't address all possible paths. So please use 
cleanup.h instead:

	union acpi_object *obj __free(kfree) = buffer.pointer;

And don't forget to add the #include.

>  	return 0;
>  #else
>  	return -ENODEV;
> 

-- 
 i.

Re: [PATCH net] platform/x86: intel_pmc_ipc: fix ACPI buffer memory leak

[Andrew Lunn]

> Good catch but this fix doesn't address all possible paths. So please use 
> cleanup.h instead:
> 
> 	union acpi_object *obj __free(kfree) = buffer.pointer;
> 
> And don't forget to add the #include.

https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html

  1.6.5. Using device-managed and cleanup.h constructs¶

  Low level cleanup constructs (such as __free()) can be used when
  building APIs and helpers, especially scoped iterators. However,
  direct use of __free() within networking core and drivers is
  discouraged. Similar guidance applies to declaring variables
  mid-function.

    Andrew

---
pw-bot: cr

RE: [PATCH net] platform/x86: intel_pmc_ipc: fix ACPI buffer memory leak

[Liu, Yongxin]

> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: Tuesday, November 25, 2025 8:30
> To: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Cc: Liu, Yongxin <Yongxin.Liu@windriver.com>; LKML <linux-
> kernel@vger.kernel.org>; Netdev <netdev@vger.kernel.org>;
> david.e.box@linux.intel.com; chao.qin@intel.com;
> yong.liang.choong@linux.intel.com; kuba@kernel.org; platform-driver-
> x86@vger.kernel.org; stable@vger.kernel.org
> Subject: Re: [PATCH net] platform/x86: intel_pmc_ipc: fix ACPI buffer
> memory leak
> 
> CAUTION: This email comes from a non Wind River email account!
> Do not click links or open attachments unless you recognize the sender and
> know the content is safe.
> 
> > Good catch but this fix doesn't address all possible paths. So please
> > use cleanup.h instead:
> >
> >       union acpi_object *obj __free(kfree) = buffer.pointer;
> >
> > And don't forget to add the #include.
> 
> https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html
> 
>   1.6.5. Using device-managed and cleanup.h constructs¶
> 
>   Low level cleanup constructs (such as __free()) can be used when
>   building APIs and helpers, especially scoped iterators. However,
>   direct use of __free() within networking core and drivers is
>   discouraged. Similar guidance applies to declaring variables
>   mid-function.
> 
>     Andrew

Thank you Ilpo and Andrew for your valuable review.
I will send a V2 to cover all possible paths.


Thanks,
Yongxin

> 
> ---
> pw-bot: cr