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Subject[PATCH v3] bus: fsl-mc: fix invalid free in fsl_mc_device_add
Date
From: Tom Rix <trix@redhat.com>

clang static analysis flags this error

fsl-mc-bus.c:695:2: warning: Attempt to free released memory [unix.Malloc]
kfree(mc_dev);
^~~~~~~~~~~~~

The problem block of code is

mc_bus = kzalloc(sizeof(*mc_bus), GFP_KERNEL);
if (!mc_bus)
return -ENOMEM;

mc_dev = &mc_bus->mc_dev;

mc_bus's structure contains a mc_dev element,
freeing it later is not appropriate.

So check if mc_bus was allocated before freeing mc_dev

This is a case where checkpatch

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

is wrong.

Fixes: a042fbed0290 ("staging: fsl-mc: simplify couple of deallocations")

Signed-off-by: Tom Rix <trix@redhat.com>
---
v1: add a comment to explain freeing uniqueness
v2: add gregkh's suggestion to comment.

drivers/bus/fsl-mc/fsl-mc-bus.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index 40526da5c6a6..839d96d03f0d 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -691,8 +691,16 @@ 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);
+ /*
+ * mc_bus allocates a private version of mc_dev
+ * it is not appropriate to free the private version.
+ * Which means we have to check the pointer before freeing it.
+ * Do not remove this check.
+ */
+ if (mc_bus)
+ kfree(mc_bus);
+ else
+ kfree(mc_dev);

return error;
}
--
2.18.1
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