[bug report] spi: stm32: properly fail on dma_request_chan error

[Dan Carpenter <dan.carpenter@linaro.org>]

[ Smatch checking is paused while we raise funding.  #SadFace
  https://lore.kernel.org/all/aTaiGSbWZ9DJaGo7@stanley.mountain/ -dan ]

Hello Alain Volmat,

Commit c266d19b7d4e ("spi: stm32: properly fail on dma_request_chan
error") from Dec 18, 2025 (linux-next), leads to the following Smatch
static checker warning:

	drivers/spi/spi-stm32.c:2578 stm32_spi_probe()
	error: 'spi->dma_rx' dereferencing possible ERR_PTR()

drivers/spi/spi-stm32.c
    2480         if (STM32_SPI_DEVICE_MODE(spi))
    2481                 ctrl->target_abort = stm32h7_spi_device_abort;
    2482 
    2483         spi->dma_tx = dma_request_chan(spi->dev, "tx");
    2484         if (IS_ERR(spi->dma_tx)) {
    2485                 ret = PTR_ERR(spi->dma_tx);
    2486                 if (ret == -ENODEV) {
    2487                         dev_info(&pdev->dev, "tx dma disabled\n");
    2488                         spi->dma_tx = NULL;
    2489                 } else {
    2490                         dev_err_probe(&pdev->dev, ret, "failed to request tx dma channel\n");
    2491                         goto err_clk_disable;
    2492                 }
    2493         } else {
    2494                 ctrl->dma_tx = spi->dma_tx;
    2495         }
    2496 
    2497         spi->dma_rx = dma_request_chan(spi->dev, "rx");
    2498         if (IS_ERR(spi->dma_rx)) {
    2499                 ret = PTR_ERR(spi->dma_rx);
    2500                 if (ret == -ENODEV) {
    2501                         dev_info(&pdev->dev, "rx dma disabled\n");
    2502                         spi->dma_rx = NULL;
    2503                 } else {
    2504                         dev_err_probe(&pdev->dev, ret, "failed to request rx dma channel\n");
    2505                         goto err_dma_release;

spi->dma_rx is an erorr pointer at this goto so it will crash.

    2506                 }
    2507         } else {
    2508                 ctrl->dma_rx = spi->dma_rx;
    2509         }
    2510 
    2511         if (spi->dma_tx || spi->dma_rx)
    2512                 ctrl->can_dma = stm32_spi_can_dma;
    2513 
    2514         spi->sram_pool = of_gen_pool_get(pdev->dev.of_node, "sram", 0);
    2515         if (spi->sram_pool) {
    2516                 spi->sram_rx_buf_size = gen_pool_size(spi->sram_pool);
    2517                 dev_info(&pdev->dev, "SRAM pool: %zu KiB for RX DMA/MDMA chaining\n",
    2518                          spi->sram_rx_buf_size / 1024);
    2519                 spi->sram_rx_buf = gen_pool_dma_zalloc(spi->sram_pool, spi->sram_rx_buf_size,
    2520                                                        &spi->sram_dma_rx_buf);
    2521                 if (!spi->sram_rx_buf) {
    2522                         dev_err(&pdev->dev, "failed to allocate SRAM buffer\n");
    2523                 } else {
    2524                         spi->mdma_rx = dma_request_chan(spi->dev, "rxm2m");
    2525                         if (IS_ERR(spi->mdma_rx)) {
    2526                                 ret = PTR_ERR(spi->mdma_rx);
    2527                                 spi->mdma_rx = NULL;
    2528                                 if (ret == -EPROBE_DEFER) {
    2529                                         goto err_pool_free;
    2530                                 } else {
    2531                                         gen_pool_free(spi->sram_pool,
    2532                                                       (unsigned long)spi->sram_rx_buf,
    2533                                                       spi->sram_rx_buf_size);
    2534                                         dev_warn(&pdev->dev,
    2535                                                  "failed to request rx mdma channel, DMA only\n");
    2536                                 }
    2537                         }
    2538                 }
    2539         }
    2540 
    2541         pm_runtime_set_autosuspend_delay(&pdev->dev,
    2542                                          STM32_SPI_AUTOSUSPEND_DELAY);
    2543         pm_runtime_use_autosuspend(&pdev->dev);
    2544         pm_runtime_set_active(&pdev->dev);
    2545         pm_runtime_get_noresume(&pdev->dev);
    2546         pm_runtime_enable(&pdev->dev);
    2547 
    2548         ret = spi_register_controller(ctrl);
    2549         if (ret) {
    2550                 dev_err(&pdev->dev, "spi controller registration failed: %d\n",
    2551                         ret);
    2552                 goto err_pm_disable;
    2553         }
    2554 
    2555         pm_runtime_put_autosuspend(&pdev->dev);
    2556 
    2557         dev_info(&pdev->dev, "driver initialized (%s mode)\n",
    2558                  STM32_SPI_HOST_MODE(spi) ? "host" : "device");
    2559 
    2560         return 0;
    2561 
    2562 err_pm_disable:
    2563         pm_runtime_disable(&pdev->dev);
    2564         pm_runtime_put_noidle(&pdev->dev);
    2565         pm_runtime_set_suspended(&pdev->dev);
    2566         pm_runtime_dont_use_autosuspend(&pdev->dev);
    2567 
    2568         if (spi->mdma_rx)
    2569                 dma_release_channel(spi->mdma_rx);
    2570 err_pool_free:
    2571         if (spi->sram_pool)
    2572                 gen_pool_free(spi->sram_pool, (unsigned long)spi->sram_rx_buf,
    2573                               spi->sram_rx_buf_size);
    2574 err_dma_release:
    2575         if (spi->dma_tx)
    2576                 dma_release_channel(spi->dma_tx);
    2577         if (spi->dma_rx)
--> 2578                 dma_release_channel(spi->dma_rx);
                                             ^^^^^^^^^^^
Here.

    2579 err_clk_disable:
    2580         clk_disable_unprepare(spi->clk);
    2581 
    2582         return ret;
    2583 }

regards,
dan carpenter