[PATCH v3] bus: fsl-mc: fix invalid free in fsl_mc_device_add
From: trix
Date: Thu Jul 09 2020 - 11:31:37 EST
From: Tom Rix <trix@xxxxxxxxxx>
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@xxxxxxxxxx>
---
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