[PATCH v3 2/4] arm_mpam: Check whether the config array is allocated before destroying it

[James Morse <james.morse@arm.com>]

__destroy_component_cfg() is called to free the configuration array.
It uses the embedded 'garbage' structure, which means the array has
to be allocated.

If __destroy_component_cfg() is called from mpam_disable() before the
configuration was ever allocated, then a NULL pointer is dereferenced.

Check for this case and return early if the configuration is not
allocated.

__destroy_component_cfg() also frees the mbwu_state as this is allocated
by __allocate_component_cfg(). As the mbwu_state is allocated after
comp->cfg is set, and is also under mpam_list_lock, only the first
pointer needs checking.

Fixes: 3bd04fe7d807bb ("arm_mpam: Extend reset logic to allow devices to be reset any time")
Signed-off-by: James Morse <james.morse@arm.com>
---
 drivers/resctrl/mpam_devices.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index bef5e9e9e844..916d8fd45ed5 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -2591,6 +2591,9 @@ static void __destroy_component_cfg(struct mpam_component *comp)
 
 	lockdep_assert_held(&mpam_list_lock);
 
+	if (!comp->cfg)
+		return;
+
 	add_to_garbage(comp->cfg);
 	list_for_each_entry(vmsc, &comp->vmsc, comp_list) {
 		msc = vmsc->msc;
-- 
2.53.0