PM: EM: Add to em_pd_list only when no failure

When em_create_perf_table() returns failure, pd is freed, there dev->em_pd
is not valid. Then accessing dev->em_pd->node will trigger kernel panic
in em_dev_register_pd_no_update(). So return early if 'ret' is non-zero.

Kernel dump:
cpu cpu0: EM: invalid power: 0
Unable to handle kernel NULL pointer dereference at virtual address
0000000000000008
Mem abort info:
pc : em_dev_register_pd_no_update+0xb4/0x79c
lr : em_dev_register_pd_no_update+0x9c/0x79c
Call trace:
 em_dev_register_pd_no_update+0xb4/0x79c (P)
 em_dev_register_perf_domain+0x18/0x58
 scmi_cpufreq_register_em+0x84/0xb8
 cpufreq_online+0x48c/0xb74
 cpufreq_add_dev+0x80/0x98
 subsys_interface_register+0x100/0x11c
 cpufreq_register_driver+0x158/0x278
 scmi_cpufreq_probe+0x1f8/0x2e0
 scmi_dev_probe+0x28/0x3c
 really_probe+0xbc/0x29c
 __driver_probe_device+0x78/0x12c
 driver_probe_device+0x3c/0x15c
 __device_attach_driver+0xb8/0x134
 bus_for_each_drv+0x84/0xe4

Fixes: cbe5aeedecc7 ("PM: EM: Assign a unique ID when creating a performance domain")
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Changwoo Min <changwoo@igalia.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/20251028-fix-energy-v1-1-ab854fd6a97c@nxp.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index e669d5057fca6da9612575a1c626474e60e7f7c4..11af9f64aa8276e47e0a5b2d615b227368af5480 100644 (file)
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -693,13 +693,16 @@ int em_dev_register_pd_no_update(struct device *dev, unsigned int nr_states,
 
 unlock:
        mutex_unlock(&em_pd_mutex);
+       if (ret)
+               return ret;
 
        mutex_lock(&em_pd_list_mutex);
        list_add_tail(&dev->em_pd->node, &em_pd_list);
        mutex_unlock(&em_pd_list_mutex);
 
        em_notify_pd_created(dev->em_pd);
-       return ret;
+
+       return 0;
 }
 EXPORT_SYMBOL_GPL(em_dev_register_pd_no_update);