linux-kernel - Re: [PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev

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Date: Fri, 17 May 2024 15:56:38 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Zhang Rui <rui.zhang@...el.com>, platform-driver-x86@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
 error27@...il.com
Subject: Re: [PATCH] platform/x86: ISST: fix use-after-free in
 tpmi_sst_dev_remove()

Hi,

On 5/14/24 11:26 AM, Harshit Mogalapalli wrote:
> In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being freed. Fix this by reordering the kfree() post the dereference.
> 
> Fixes: 9d1d36268f3d ("platform/x86: ISST: Support partitioned systems")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>

This looks obviously correct to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Still would be nice if one of the Intel maintainers for this
can ack it.

Either way I'll merge this for the first pdx86 fixes pull-request
for 6.10 (when I get around to merging the first round of fixes).

Regards,

Hans




> ---
> This is found by smatch and only compile tested.
> ---
>  drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> index 7bac7841ff0a..7fa360073f6e 100644
> --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> @@ -1610,8 +1610,8 @@ void tpmi_sst_dev_remove(struct auxiliary_device *auxdev)
>  	tpmi_sst->partition_mask_current &= ~BIT(plat_info->partition);
>  	/* Free the package instance when the all partitions are removed */
>  	if (!tpmi_sst->partition_mask_current) {
> -		kfree(tpmi_sst);
>  		isst_common.sst_inst[tpmi_sst->package_id] = NULL;
> +		kfree(tpmi_sst);
>  	}
>  	mutex_unlock(&isst_tpmi_dev_lock);
>  }