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

[Ilpo Järvinen]

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

> From: Yongxin Liu <yongxin.liu@xxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxx
> Fixes: 7e2f7e25f6ff ("arch: x86: add IPC mailbox accessor function and add SoC register access")
> Signed-off-by: Yongxin Liu <yongxin.liu@xxxxxxxxxxxxx>
> ---
>  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.