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SubjectRE: [PATCH] dmaengine: imx-sdma: fix use-after-free on probe error path
Date
Reviewed-by: Robin Gong <yibin.gong@nxp.com>
> -----Original Message-----
> From: Sven Van Asbroeck <thesven73@gmail.com>
> Subject: [PATCH] dmaengine: imx-sdma: fix use-after-free on probe error path
>
> If probe() fails anywhere beyond the point where
> sdma_get_firmware() is called, then a kernel oops may occur.
>
> Problematic sequence of events:
> 1. probe() calls sdma_get_firmware(), which schedules the
> firmware callback to run when firmware becomes available,
> using the sdma instance structure as the context 2. probe() encounters an
> error, which deallocates the
> sdma instance structure
> 3. firmware becomes available, firmware callback is
> called with deallocated sdma instance structure 4. use after free - kernel
> oops !
>
> Solution: only attempt to load firmware when we're certain that probe() will
> succeed. This guarantees that the firmware callback's context will remain valid.
>
> Note that the remove() path is unaffected by this issue: the firmware loader will
> increment the driver module's use count, ensuring that the module cannot be
> unloaded while the firmware callback is pending or running.
>
> To: Robin Gong <yibin.gong@nxp.com>
> Cc: Vinod Koul <vkoul@kernel.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
> Cc: Fabio Estevam <festevam@gmail.com>
> Cc: NXP Linux Team <linux-imx@nxp.com>
> Cc: dmaengine@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
> ---
> drivers/dma/imx-sdma.c | 48 ++++++++++++++++++++++++------------------
> 1 file changed, 27 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c index
> 99d9f431ae2c..3f0f41d16e1c 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -2096,27 +2096,6 @@ static int sdma_probe(struct platform_device
> *pdev)
> if (pdata && pdata->script_addrs)
> sdma_add_scripts(sdma, pdata->script_addrs);
>
> - if (pdata) {
> - ret = sdma_get_firmware(sdma, pdata->fw_name);
> - if (ret)
> - dev_warn(&pdev->dev, "failed to get firmware from platform
> data\n");
> - } else {
> - /*
> - * Because that device tree does not encode ROM script address,
> - * the RAM script in firmware is mandatory for device tree
> - * probe, otherwise it fails.
> - */
> - ret = of_property_read_string(np, "fsl,sdma-ram-script-name",
> - &fw_name);
> - if (ret)
> - dev_warn(&pdev->dev, "failed to get firmware name\n");
> - else {
> - ret = sdma_get_firmware(sdma, fw_name);
> - if (ret)
> - dev_warn(&pdev->dev, "failed to get firmware from device
> tree\n");
> - }
> - }
> -
> sdma->dma_device.dev = &pdev->dev;
>
> sdma->dma_device.device_alloc_chan_resources =
> sdma_alloc_chan_resources; @@ -2161,6 +2140,33 @@ static int
> sdma_probe(struct platform_device *pdev)
> of_node_put(spba_bus);
> }
>
> + /*
> + * Kick off firmware loading as the very last step:
> + * attempt to load firmware only if we're not on the error path, because
> + * the firmware callback requires a fully functional and allocated sdma
> + * instance.
> + */
> + if (pdata) {
> + ret = sdma_get_firmware(sdma, pdata->fw_name);
> + if (ret)
> + dev_warn(&pdev->dev, "failed to get firmware from platform
> data\n");
> + } else {
> + /*
> + * Because that device tree does not encode ROM script address,
> + * the RAM script in firmware is mandatory for device tree
> + * probe, otherwise it fails.
> + */
> + ret = of_property_read_string(np, "fsl,sdma-ram-script-name",
> + &fw_name);
> + if (ret)
> + dev_warn(&pdev->dev, "failed to get firmware name\n");
> + else {
> + ret = sdma_get_firmware(sdma, fw_name);
> + if (ret)
> + dev_warn(&pdev->dev, "failed to get firmware from device
> tree\n");
> + }
> + }
> +
> return 0;
>
> err_register:
> --
> 2.17.1

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