linux-kernel - [PATCH v2] platform/x86: ISST: fix use-after-free in tpmi_sst_dev

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Date: Fri, 17 May 2024 07:49:46 -0700
From: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.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, harshit.m.mogalapalli@...cle.com
Subject: [PATCH v2] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

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>
Reviewed-by: Hans de Goede <hdegoede@...hat.com>
---
v1->v2: Add R.B from Hans and fix commit message wrapping to 75 chars.
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);
 }
-- 
2.39.3