Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] platform/x86/intel/ifs: build_cpugroup_mask() called before cpu_online() check --
commit 206d196a9743b86ac3f7ca97505586f73d04016c Author: Jithu Joseph <[email protected]> platform/x86/intel/ifs: Select CPUs from topology_cluster_cpumask() for simultaneous IFS tests This commit updates the intel_ifs driver to record the group of CPUs tested simultaneously in ifsd->grp_cpumask using topology_cluster_cpumask() and stop_cluster_cpuslocked() when ifsd->all_lp_join is set. > diff --git a/drivers/platform/x86/intel/ifs/runtest.c > b/drivers/platform/x86/intel/ifs/runtest.c > index c6a4d6dcccf1f..09e7a81e92204 100644 > --- a/drivers/platform/x86/intel/ifs/runtest.c > +++ b/drivers/platform/x86/intel/ifs/runtest.c [ ... ] > @@ -398,6 +407,24 @@ static void ifs_array_test_gen1(int cpu, struct device > *dev) > ifsd->status = SCAN_TEST_PASS; > } > > +static void build_cpugroup_mask(struct device *dev, int cpu) > +{ > + struct ifs_data *ifsd = ifs_get_data(dev); > + > + cpumask_clear(&ifsd->grp_cpumask); > + > + /* > + * Some CPUs, such as Sierra Forest and Clearwater Forest, have > multiple cores > + * sharing the same SCAN test engine, but they don't require a > rendezvous. > + */ > + if (!ifsd->all_lp_join) { > + cpumask_set_cpu(cpu, &ifsd->grp_cpumask); > + return; > + } > + > + cpumask_copy(&ifsd->grp_cpumask, topology_cluster_cpumask(cpu)); > +} > + > /* > * Initiate per core test. It wakes up work queue threads on the target CPU > and > * its sibling CPU. Once all sibling threads wake up, the scan test gets > executed and > @@ -411,6 +438,7 @@ int do_core_test(int cpu, struct device *dev) > > /* Prevent CPUs from being taken offline during the scan test */ > cpus_read_lock(); > + build_cpugroup_mask(dev, cpu); > > if (!cpu_online(cpu)) { > dev_info(dev, "cannot test on the offline CPU %d\n", cpu); [Severity: High] Should build_cpugroup_mask(dev, cpu) be called after the !cpu_online(cpu) check in do_core_test() rather than before it? In drivers/platform/x86/intel/ifs/sysfs.c, run_test_store() only checks that cpu < nr_cpu_ids before invoking do_core_test(cpu, dev): drivers/platform/x86/intel/ifs/sysfs.c:run_test_store() { ... rc = kstrtouint(buf, 0, &cpu); if (rc < 0 || cpu >= nr_cpu_ids) return -EINVAL; rc = mutex_lock_interruptible(&ifs_sem); if (rc) return rc; rc = do_core_test(cpu, dev); ... } However, in arch/x86/kernel/smpboot.c, smp_prepare_cpus_common() only allocates per_cpu(cpu_l2c_shared_map, cpu) for CPUs in cpu_possible_mask: arch/x86/kernel/smpboot.c:smp_prepare_cpus_common() { ... for_each_possible_cpu(cpu) { node = cpu_to_node(cpu); ... zalloc_cpumask_var_node(&per_cpu(cpu_l2c_shared_map, cpu), GFP_KERNEL, node); } } If userspace writes a CPU index that is less than nr_cpu_ids but not in cpu_possible_mask (for example when CONFIG_FORCE_NR_CPUS=y or when cpu_possible_mask is sparse), calling build_cpugroup_mask() before checking cpu_online(cpu) will invoke: build_cpugroup_mask() topology_cluster_cpumask(cpu) cpu_clustergroup_mask(cpu) cpu_l2c_shared_mask(cpu) per_cpu(cpu_l2c_shared_map, cpu) Can this access an uninitialized per-CPU offset and dereference a NULL cpumask_var_t pointer under CONFIG_CPUMASK_OFFSTACK=y (or set a non-possible CPU bit in ifsd->grp_cpumask when ifsd->all_lp_join is false, which later sysfs readers in this series pass to per_cpu_ptr(ifsd->result_ptr, lcpu))? Additionally, when a valid possible CPU is offline, remove_siblinginfo() clears cpu_l2c_shared_mask(cpu). If userspace attempts to run a test on an offline CPU and do_core_test() returns -EINVAL, won't calling build_cpugroup_mask() beforehand overwrite ifsd->grp_cpumask with an empty mask (when ifsd->all_lp_join is true) or with the untested offline CPU (when ifsd->all_lp_join is false), clobbering the previous test's CPU group state exposed by cpus_ran_list, status_list, details_list, and addnl_details_list added in the subsequent patches? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=9
