PM: EM: Fix NULL pointer dereference when perf domain ID is not found

PM: EM: Fix NULL pointer dereference when perf domain ID is not found

dev_energymodel_nl_get_perf_domains_doit() calls
em_perf_domain_get_by_id() but does not check the return value before
passing it to __em_nl_get_pd_size(). When a caller supplies a
non-existent perf domain ID, em_perf_domain_get_by_id() returns NULL,
and __em_nl_get_pd_size() immediately dereferences pd->cpus
(struct offset 0x30), causing a NULL pointer dereference.

The sister handler dev_energymodel_nl_get_perf_table_doit() already
handles this correctly via __em_nl_get_pd_table_id(), which returns
NULL and causes the caller to return -EINVAL. Add the same NULL check
in the get-perf-domains do handler.

Fixes: 380ff27af25e ("PM: EM: Add dump to get-perf-domains in the EM YNL spec")
Reported-by: Yi Lai <yi1.lai@linux.intel.com>
Closes: https://lore.kernel.org/lkml/aXiySM79UYfk+ytd@ly-workstation/
Signed-off-by: Changwoo Min <changwoo@igalia.com>
Cc: 6.19+ <stable@vger.kernel.org> # 6.19+
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20260329073615.649976-1-changwoo@igalia.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>