Re: [PATCH 3/3] HID: bpf: lazy load the hid_tail_call entrypoint
From: Benjamin Tissoires
Date: Thu Apr 25 2024 - 08:53:02 EST
On Apr 24 2024, Benjamin Tissoires wrote:
> On Apr 23 2024, Dan Carpenter wrote:
> > Hi Benjamin,
> >
> > kernel test robot noticed the following build warnings:
> >
> > url: https://github.com/intel-lab-lkp/linux/commits/Benjamin-Tissoires/HID-bpf-fix-a-comment-in-a-define/20240419-225110
> > base: b912cf042072e12e93faa874265b30cc0aa521b9
> > patch link: https://lore.kernel.org/r/20240419-hid_bpf_lazy_skel-v1-3-9210bcd4b61c%40kernel.org
> > patch subject: [PATCH 3/3] HID: bpf: lazy load the hid_tail_call entrypoint
> > config: i386-randconfig-141-20240423 (https://download.01.org/0day-ci/archive/20240423/202404231109.h2IRrMMD-lkp@xxxxxxxxx/config)
> > compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > | Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > | Closes: https://lore.kernel.org/r/202404231109.h2IRrMMD-lkp@xxxxxxxxx/
> >
> > smatch warnings:
> > drivers/hid/bpf/hid_bpf_jmp_table.c:478 __hid_bpf_attach_prog() error: uninitialized symbol 'link'.
> >
> > vim +/link +478 drivers/hid/bpf/hid_bpf_jmp_table.c
> >
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 396 noinline int
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 397 __hid_bpf_attach_prog(struct hid_device *hdev, enum hid_bpf_prog_type prog_type,
> > 7cdd2108903a4e3 Benjamin Tissoires 2024-01-24 398 int prog_fd, struct bpf_prog *prog, __u32 flags)
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 399 {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 400 struct bpf_link_primer link_primer;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 401 struct hid_bpf_link *link;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 402 struct hid_bpf_prog_entry *prog_entry;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 403 int cnt, err = -EINVAL, prog_table_idx = -1;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 404
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 405 mutex_lock(&hid_bpf_attach_lock);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 406
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19 407 if (!jmp_table.map) {
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19 408 err = hid_bpf_preload_skel();
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19 409 WARN_ONCE(err, "error while preloading HID BPF dispatcher: %d", err);
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19 410 if (err)
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19 411 goto err_unlock;
> > ^^^^^^^^^^^^^^^^
> > link isn't initialized.
>
> Well spotted! Thanks
> I'll send a v2 soon.
FWIW, this patch prevents the proper unloading of the HID-BPF programs.
So not sure we'll want it as such just now.
Cheers,
Benjamin
> >
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19 412 }
> > 60caa381da7dc38 Benjamin Tissoires 2024-04-19 413
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 414 link = kzalloc(sizeof(*link), GFP_USER);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 415 if (!link) {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 416 err = -ENOMEM;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 417 goto err_unlock;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 418 }
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 419
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 420 bpf_link_init(&link->link, BPF_LINK_TYPE_UNSPEC,
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 421 &hid_bpf_link_lops, prog);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 422
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 423 /* do not attach too many programs to a given HID device */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 424 cnt = hid_bpf_program_count(hdev, NULL, prog_type);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 425 if (cnt < 0) {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 426 err = cnt;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 427 goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 428 }
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 429
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 430 if (cnt >= hid_bpf_max_programs(prog_type)) {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 431 err = -E2BIG;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 432 goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 433 }
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 434
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 435 prog_table_idx = hid_bpf_insert_prog(prog_fd, prog);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 436 /* if the jmp table is full, abort */
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 437 if (prog_table_idx < 0) {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 438 err = prog_table_idx;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 439 goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 440 }
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 441
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 442 if (flags & HID_BPF_FLAG_INSERT_HEAD) {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 443 /* take the previous prog_entry slot */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 444 jmp_table.tail = PREV(jmp_table.tail);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 445 prog_entry = &jmp_table.entries[jmp_table.tail];
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 446 } else {
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 447 /* take the next prog_entry slot */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 448 prog_entry = &jmp_table.entries[jmp_table.head];
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 449 jmp_table.head = NEXT(jmp_table.head);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 450 }
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 451
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 452 /* we steal the ref here */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 453 prog_entry->prog = prog;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 454 prog_entry->idx = prog_table_idx;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 455 prog_entry->hdev = hdev;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 456 prog_entry->type = prog_type;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 457
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 458 /* finally store the index in the device list */
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 459 err = hid_bpf_populate_hdev(hdev, prog_type);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 460 if (err) {
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 461 hid_bpf_release_prog_at(prog_table_idx);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 462 goto err_unlock;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 463 }
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 464
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 465 link->hid_table_index = prog_table_idx;
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 466
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 467 err = bpf_link_prime(&link->link, &link_primer);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 468 if (err)
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 469 goto err_unlock;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 470
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 471 mutex_unlock(&hid_bpf_attach_lock);
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 472
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 473 return bpf_link_settle(&link_primer);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 474
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 475 err_unlock:
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 476 mutex_unlock(&hid_bpf_attach_lock);
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 477
> > 4b9a3f49f02bf68 Benjamin Tissoires 2023-01-13 @478 kfree(link);
> > ^^^^
> >
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 479
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 480 return err;
> > f5c27da4e3c8a2e Benjamin Tissoires 2022-11-03 481 }
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
> >