linux-kernel - Re: [PATCH v3] platform/x86: intel_pmc

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Message-ID: <42e5a7c5-4d18-4e89-07c0-fdfb2b3bc28e@linux.intel.com>
Date: Fri, 28 Nov 2025 11:54:08 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: yongxin.liu@...driver.com
cc: platform-driver-x86@...r.kernel.org, david.e.box@...ux.intel.com, 
    LKML <linux-kernel@...r.kernel.org>, andrew@...n.ch, kuba@...nel.org, 
    stable@...r.kernel.org
Subject: Re: [PATCH v3] platform/x86: intel_pmc_ipc: fix ACPI buffer memory
 leak

On Fri, 28 Nov 2025, yongxin.liu@...driver.com wrote:

> From: Yongxin Liu <yongxin.liu@...driver.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 __free(kfree) for ACPI object to properly release the allocated buffer.
> 
> Cc: stable@...r.kernel.org
> Fixes: 7e2f7e25f6ff ("arch: x86: add IPC mailbox accessor function and add SoC register access")
> Signed-off-by: Yongxin Liu <yongxin.liu@...driver.com>
> ---
> V2->V3:
> Use __free(kfree) instead of goto and kfree();
> 
> V1->V2:
> Cover all potential paths for kfree();
> ---
>  include/linux/platform_data/x86/intel_pmc_ipc.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/platform_data/x86/intel_pmc_ipc.h b/include/linux/platform_data/x86/intel_pmc_ipc.h
> index 1d34435b7001..cf0b78048b0e 100644
> --- a/include/linux/platform_data/x86/intel_pmc_ipc.h
> +++ b/include/linux/platform_data/x86/intel_pmc_ipc.h
> @@ -9,6 +9,7 @@
>  #ifndef INTEL_PMC_IPC_H
>  #define INTEL_PMC_IPC_H
>  #include <linux/acpi.h>
> +#include <linux/cleanup.h>
>  
>  #define IPC_SOC_REGISTER_ACCESS			0xAA
>  #define IPC_SOC_SUB_CMD_READ			0x00
> @@ -48,7 +49,7 @@ static inline int intel_pmc_ipc(struct pmc_ipc_cmd *ipc_cmd, struct pmc_ipc_rbuf
>  		{.type = ACPI_TYPE_INTEGER,},
>  	};
>  	struct acpi_object_list arg_list = { PMC_IPCS_PARAM_COUNT, params };
> -	union acpi_object *obj;
> +	union acpi_object *obj __free(kfree) = NULL;

Please declare it where the value is getting assigned to it like I 
instructed in v1. While not strictly necessary here, I want us to 
reinforce the only correct pattern to use cleanup.h helpers at every
usage site.

The placement matters when there is more than once cleanup.h thing done 
within a function. The cleanup order depends on the order you declared the 
variables.

>  	int status;
>  
>  	if (!ipc_cmd || !rbuf)
> 

-- 
 i.