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SubjectRe: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference
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Hi,

On 1/29/21 6:26 PM, Mario Limonciello wrote:
> An upcoming Dell platform is causing a NULL pointer dereference
> in dell-wmi-sysman initialization. Validate that the input from
> BIOS matches correct ACPI types and abort module initialization
> if it fails.
>
> This leads to a memory leak that needs to be cleaned up properly.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> ---
> drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> index dc6dd531c996..38b497991071 100644
> --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const char *guid)
> return retval;
> /* need to use specific instance_id and guid combination to get right data */
> obj = get_wmiobj_pointer(instance_id, guid);
> - if (!obj)
> + if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> + release_attributes_data();

All calls of init_bios_attributes() have the following error handling:

ret = init_bios_attributes(INT, DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
if (ret) {
pr_debug("failed to populate integer type attributes\n");
goto fail_create_group;
}

...

fail_create_group:
release_attributes_data();

So that added release_attributes_data() call is not necessary. If you can respin
this patch Monday with the release_attributes_data(); addition dropped, then
I will try to get this to Linus in time for 5.11 .

Or I can fix this up locally if you agree with dropping the unnecessary
release_attributes_data() call.

Regards,

Hans




> return -ENODEV;
> + }
> elements = obj->package.elements;
>
> mutex_lock(&wmi_priv.mutex);
> while (elements) {
> /* sanity checking */
> + if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
> + pr_debug("incorrect element type\n");
> + goto nextobj;
> + }
> if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
> pr_debug("empty attribute found\n");
> goto nextobj;
>

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