Hello Sebastian Andrzej Siewior,
Commit 4788c861ad7e ("scftorture: Use a lock-less list to free
memory.") from Nov 8, 2024 (linux-next), leads to the following
Smatch static checker warning:
kernel/scftorture.c:393 scftorture_invoke_one()
error: we previously assumed 'scfcp' could be null (see line 382)
kernel/scftorture.c
342 static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)
343 {
344 bool allocfail = false;
345 uintptr_t cpu;
346 int ret = 0;
347 struct scf_check *scfcp = NULL;
348 struct scf_selector *scfsp = scf_sel_rand(trsp);
349
350 if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
351 scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
352 if (!scfcp) {
353 WARN_ON_ONCE(!IS_ENABLED(CONFIG_KASAN));
354 atomic_inc(&n_alloc_errs);
355 allocfail = true;
356 } else {
357 scfcp->scfc_cpu = -1;
358 scfcp->scfc_wait = scfsp->scfs_wait;
359 scfcp->scfc_out = false;
360 scfcp->scfc_rpc = false;
361 }
362 }
363 if (use_cpus_read_lock)
364 cpus_read_lock();
365 else
366 preempt_disable();
367 switch (scfsp->scfs_prim) {
368 case SCF_PRIM_RESCHED:
369 if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
370 cpu = torture_random(trsp) % nr_cpu_ids;
371 scfp->n_resched++;
372 resched_cpu(cpu);
373 this_cpu_inc(scf_invoked_count);
374 }
375 break;
376 case SCF_PRIM_SINGLE:
377 cpu = torture_random(trsp) % nr_cpu_ids;
378 if (scfsp->scfs_wait)
379 scfp->n_single_wait++;
380 else
381 scfp->n_single++;
382 if (scfcp) {
This code assumes that scfcp can be NULL.
383 scfcp->scfc_cpu = cpu;
384 barrier(); // Prevent race-reduction compiler optimizations.
385 scfcp->scfc_in = true;
386 }
387 ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, scfsp->scfs_wait);
388 if (ret) {
389 if (scfsp->scfs_wait)
390 scfp->n_single_wait_ofl++;
391 else
392 scfp->n_single_ofl++;
--> 393 scf_add_to_free_list(scfcp);
Originally this was a kfree(scfcp) which can accept a NULL, but
scf_add_to_free_list() can't handle a NULL parameter.
394 scfcp = NULL;
395 }
396 break;
397 case SCF_PRIM_SINGLE_RPC:
regards,
dan carpenter
