linux-kernel - [PATCH] bus: fsl-mc: fix double-free on mc

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Date:   Wed,  8 Nov 2023 18:45:46 +0200
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Cc:     stuyoder@...il.com, laurentiu.tudor@....com,
        Ioana Ciornei <ioana.ciornei@....com>
Subject: [PATCH] bus: fsl-mc: fix double-free on mc_dev

The blamed commit tried to simplify how the deallocations are done but,
in the process, introduced a double-free on the mc_dev variable.

In case the MC device is a DPRC, a new mc_bus is allocated and the
mc_dev variable is just a reference to one of its fields. In this
circumstance, on the error path only the mc_bus should be freed.

This commit introduces back the following checkpatch warning which is a
false-positive.

WARNING: kfree(NULL) is safe and this check is probably not required
+       if (mc_bus)
+               kfree(mc_bus);

Fixes: a042fbed0290 ("staging: fsl-mc: simplify couple of deallocations")
Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
---
 drivers/bus/fsl-mc/fsl-mc-bus.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index 2f6d5002e43d..b405ee330af1 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -905,8 +905,10 @@ int fsl_mc_device_add(struct fsl_mc_obj_desc *obj_desc,
 
 error_cleanup_dev:
 	kfree(mc_dev->regions);
-	kfree(mc_bus);
-	kfree(mc_dev);
+	if (mc_bus)
+		kfree(mc_bus);
+	else
+		kfree(mc_dev);
 
 	return error;
 }
-- 
2.25.1