Am 2021-07-06 um 11:36 a.m. schrieb Colin Ian King:
> Hi,
>
> Static analysis with Coverity on linux-next has found a potential null
> pointer dereference in function svm_range_restore_pages in
> drivers/gpu/drm/amd/amdkfd/kfd_svm.c from the following commit:
>
> commit d4ebc2007040a0aff01bfe1b194085d3867328fd
> Author: Philip Yang <Philip.Yang@xxxxxxx>
> Date: Tue Jun 22 00:12:32 2021 -0400
>
> drm/amdkfd: implement counters for vm fault and migration
>
> The analysis is as follows:
Thanks. Philip, see inline ...
>
> 2397 int
> 2398 svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
> 2399 uint64_t addr)
> 2400{
> 2401 struct mm_struct *mm = NULL;
> 2402 struct svm_range_list *svms;
> 2403 struct svm_range *prange;
> 2404 struct kfd_process *p;
> 2405 uint64_t timestamp;
> 2406 int32_t best_loc;
> 2407 int32_t gpuidx = MAX_GPU_INSTANCE;
> 2408 bool write_locked = false;
> 2409 int r = 0;
> 2410
>
> 1. Condition !(adev->kfd.dev->pgmap.type != 0), taking false branch.
>
> 2411 if (!KFD_IS_SVM_API_SUPPORTED(adev->kfd.dev)) {
> 2412 pr_debug("device does not support SVM\n");
> 2413 return -EFAULT;
> 2414 }
> 2415
> 2416 p = kfd_lookup_process_by_pasid(pasid);
>
> 2. Condition !p, taking false branch.
>
> 2417 if (!p) {
> 2418 pr_debug("kfd process not founded pasid 0x%x\n", pasid);
> 2419 return -ESRCH;
> 2420 }
>
> 3. Condition !p->xnack_enabled, taking false branch.
>
> 2421 if (!p->xnack_enabled) {
> 2422 pr_debug("XNACK not enabled for pasid 0x%x\n", pasid);
> 2423 return -EFAULT;
> 2424 }
> 2425 svms = &p->svms;
> 2426
>
> 4. Condition 0 /* __builtin_types_compatible_p() */, taking false
> branch.
> 5. Condition 1 /* __builtin_types_compatible_p() */, taking true branch.
> 6. Falling through to end of if statement.
> 7. Condition !!branch, taking false branch.
> 8. Condition ({...; !!branch;}), taking false branch.
>
> 2427 pr_debug("restoring svms 0x%p fault address 0x%llx\n", svms,
> addr);
> 2428
> 2429 mm = get_task_mm(p->lead_thread);
>
> 9. Condition !mm, taking false branch.
>
> 2430 if (!mm) {
> 2431 pr_debug("svms 0x%p failed to get mm\n", svms);
> 2432 r = -ESRCH;
> 2433 goto out;
> 2434 }
> 2435
> 2436 mmap_read_lock(mm);
> 2437retry_write_locked:
> 2438 mutex_lock(&svms->lock);
> 2439 prange = svm_range_from_addr(svms, addr, NULL);
>
> 10. Condition !prange, taking true branch.
> 18. Condition !prange, taking true branch.
> 2440 if (!prange) {
> 11. Condition 0 /* __builtin_types_compatible_p() */, taking false
> branch.
> 12. Condition 1 /* __builtin_types_compatible_p() */, taking true
> branch.
> 13. Falling through to end of if statement.
> 14. Condition !!branch, taking false branch.
> 15. Condition ({...; !!branch;}), taking false branch.
> 19. Condition 0 /* __builtin_types_compatible_p() */, taking false
> branch.
> 20. Condition 1 /* __builtin_types_compatible_p() */, taking true
> branch.
> 21. Falling through to end of if statement.
> 22. Condition !!branch, taking false branch.
> 23. Condition ({...; !!branch;}), taking false branch.
>
> 2441 pr_debug("failed to find prange svms 0x%p address
> [0x%llx]\n",
> 2442 svms, addr);
>
> 16. Condition !write_locked, taking true branch.
> 24. Condition !write_locked, taking false branch.
>
> 2443 if (!write_locked) {
> 2444 /* Need the write lock to create new range
> with MMU notifier.
> 2445 * Also flush pending deferred work to make
> sure the interval
> 2446 * tree is up to date before we add a new range
> 2447 */
> 2448 mutex_unlock(&svms->lock);
> 2449 mmap_read_unlock(mm);
> 2450 mmap_write_lock(mm);
> 2451 write_locked = true;
>
> 17. Jumping to label retry_write_locked.
>
> 2452 goto retry_write_locked;
> 2453 }
> 2454 prange = svm_range_create_unregistered_range(adev,
> p, mm, addr);
>
> 25. Condition !prange, taking true branch.
> 26. var_compare_op: Comparing prange to null implies that prange
> might be null.
>
> 2455 if (!prange) {
>
> 27. Condition 0 /* __builtin_types_compatible_p() */, taking false
> branch.
> 28. Condition 1 /* __builtin_types_compatible_p() */, taking true
> branch.
> 29. Falling through to end of if statement.
> 30. Condition !!branch, taking false branch.
> 31. Condition ({...; !!branch;}), taking false branch.
>
> 2456 pr_debug("failed to create unregistered
> range svms 0x%p address [0x%llx]\n",
> 2457 svms, addr);
> 2458 mmap_write_downgrade(mm);
> 2459 r = -EFAULT;
>
> 32. Jumping to label out_unlock_svms.
>
> 2460 goto out_unlock_svms;
> 2461 }
> 2462 }
> 2463 if (write_locked)
> 2464 mmap_write_downgrade(mm);
> 2465
> 2466 mutex_lock(&prange->migrate_mutex);
> 2467
> 2468 if (svm_range_skip_recover(prange)) {
> 2469 amdgpu_gmc_filter_faults_remove(adev, addr, pasid);
> 2470 goto out_unlock_range;
> 2471 }
> 2472
> 2473 timestamp = ktime_to_us(ktime_get()) -
> prange->validate_timestamp;
> 2474 /* skip duplicate vm fault on different pages of same range */
> 2475 if (timestamp < AMDGPU_SVM_RANGE_RETRY_FAULT_PENDING) {
> 2476 pr_debug("svms 0x%p [0x%lx %lx] already restored\n",
> 2477 svms, prange->start, prange->last);
> 2478 goto out_unlock_range;
> 2479 }
> 2480
> 2481 best_loc = svm_range_best_restore_location(prange, adev,
> &gpuidx);
> 2482 if (best_loc == -1) {
> 2483 pr_debug("svms %p failed get best restore loc [0x%lx
> 0x%lx]\n",
> 2484 svms, prange->start, prange->last);
> 2485 r = -EACCES;
> 2486 goto out_unlock_range;
> 2487 }
> 2488
> 2489 pr_debug("svms %p [0x%lx 0x%lx] best restore 0x%x, actual
> loc 0x%x\n",
> 2490 svms, prange->start, prange->last, best_loc,
> 2491 prange->actual_loc);
> 2492
> 2493 if (prange->actual_loc != best_loc) {
> 2494 if (best_loc) {
> 2495 r = svm_migrate_to_vram(prange, best_loc, mm);
> 2496 if (r) {
> 2497 pr_debug("svm_migrate_to_vram failed
> (%d) at %llx, falling back to system memory\n",
> 2498 r, addr);
> 2499 /* Fallback to system memory if
> migration to
> 2500 * VRAM failed
> 2501 */
> 2502 if (prange->actual_loc)
> 2503 r =
> svm_migrate_vram_to_ram(prange, mm);
> 2504 else
> 2505 r = 0;
> 2506 }
> 2507 } else {
> 2508 r = svm_migrate_vram_to_ram(prange, mm);
> 2509 }
> 2510 if (r) {
> 2511 pr_debug("failed %d to migrate svms %p
> [0x%lx 0x%lx]\n",
> 2512 r, svms, prange->start, prange->last);
> 2513 goto out_unlock_range;
> 2514 }
> 2515 }
> 2516
> 2517 r = svm_range_validate_and_map(mm, prange, gpuidx, false,
> false);
> 2518 if (r)
> 2519 pr_debug("failed %d to map svms 0x%p [0x%lx 0x%lx]
> to gpus\n",
> 2520 r, svms, prange->start, prange->last);
> 2521
> 2522out_unlock_range:
> 2523 mutex_unlock(&prange->migrate_mutex);
> 2524out_unlock_svms:
> 2525 mutex_unlock(&svms->lock);
> 2526 mmap_read_unlock(mm);
> 2527
>
> Dereference after null check (FORWARD_NULL)
> 33. var_deref_model: Passing null pointer prange to
> svm_range_count_fault, which dereferences it.
>
> 2528 svm_range_count_fault(adev, p, prange, gpuidx);
Looks like you need to add a NULL check for prange here.
Regards,
Felix
>
>
> The jump in line 2460 to out_unlock_svms will occur if prange is null,
> however, calling svm_range_count_fault with a null prange will cause a
> null pointer deference when it calls svm_range_get_pdd_by_adev and
> dereferences the pointer as follows:
>
> p = container_of(prange->svms, struct kfd_process, svms);
>
> Colin
>
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