From: Tom Rix <[email protected]>
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 <[email protected]>
---
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
On Thu, Jul 09, 2020 at 08:31:19AM -0700, [email protected] wrote:
> From: Tom Rix <[email protected]>
>
> 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 <[email protected]>
> ---
> 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
>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Also add a cc: stable to this please when it is applied to a tree, in
the proper place, as it fixes a bug.
thanks,
greg k-h
On 7/9/2020 6:31 PM, [email protected] wrote:
> From: Tom Rix <[email protected]>
>
> 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 <[email protected]>
> ---
> 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;
> }
>
Thanks, Tom!
Reviewed-by: Laurentiu Tudor <[email protected]>
---
Best Regards, Laurentiu