spi: fix controller registration API inconsistency

The SPI controller API is asymmetric in that a controller is allocated
and registered in two step, while it is freed as part of deregistration.
[1]

This is especially unfortunate as any driver data is freed along with
the controller, something which has lead to use-after-free bugs during
deregistration when drivers tear down resources after deregistering the
controller (or tear down resources that may still be in use before
deregistering the controller in an attempt to work around the API).

To reduce the risk of such bugs being introduced a device managed
allocation interface was added, but this arguably made things even less
consistent as now whether the controller gets freed as part of
deregistration depends on how it was allocated. [2][3]

With most drivers converted to use managed allocation in preparation for
fixing the API, the remaining 16 drivers can be converted in one
tree-wide change. Ten of those drivers use the bitbang interface and can
be converted by simply removing the extra reference already taken by
spi_bitbang_start() (and updating the two bitbang drivers that use
managed allocation). [4]

Fix the API inconsistency by no longer dropping a reference when
deregistering non-devres allocated controllers.

[1] 68b892f1fdc4 ("spi: document odd controller reference handling")
[2] 5e844cc37a5c ("spi: Introduce device-managed SPI controller allocation")
[3] 3f174274d224 ("spi: fix misleading controller deregistration kernel-doc")
[4] 702a4879ec33 ("spi: bitbang: Let spi_bitbang_start() take a reference to master")

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20260521073816.766596-1-johan@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/media/usb/msi2500/msi2500.c b/drivers/media/usb/msi2500/msi2500.c
index 1ff98956b680b139c2a2eae17014a992e4a463f1..5c512d61dc1b335f270db3e0eb4e8a34c031910b 100644 (file)
--- a/drivers/media/usb/msi2500/msi2500.c
+++ b/drivers/media/usb/msi2500/msi2500.c
@@ -575,6 +575,7 @@ static void msi2500_disconnect(struct usb_interface *intf)
        v4l2_device_disconnect(&dev->v4l2_dev);
        video_unregister_device(&dev->vdev);
        spi_unregister_controller(dev->ctlr);
+       spi_controller_put(dev->ctlr);
        mutex_unlock(&dev->v4l2_lock);
        mutex_unlock(&dev->vb_queue_lock);
 
@@ -1230,10 +1231,8 @@ static int msi2500_probe(struct usb_interface *intf,
        ctlr->transfer_one_message = msi2500_transfer_one_message;
        spi_controller_set_devdata(ctlr, dev);
        ret = spi_register_controller(ctlr);
-       if (ret) {
-               spi_controller_put(ctlr);
-               goto err_unregister_v4l2_dev;
-       }
+       if (ret)
+               goto err_put_controller;
 
        /* load v4l2 subdevice */
        sd = v4l2_spi_new_subdev(&dev->v4l2_dev, ctlr, &board_info);
@@ -1276,6 +1275,8 @@ err_free_controls:
        v4l2_ctrl_handler_free(&dev->hdl);
 err_unregister_controller:
        spi_unregister_controller(dev->ctlr);
+err_put_controller:
+       spi_controller_put(dev->ctlr);
 err_unregister_v4l2_dev:
        v4l2_device_unregister(&dev->v4l2_dev);
 err_free_mem:

diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
index 9f03ac217319c5f4ca0b8d0ed87b880642b2562e..fb288ed56d94f91e3968849f26cb6783fffe7883 100644 (file)
--- a/drivers/spi/spi-bitbang.c
+++ b/drivers/spi/spi-bitbang.c
@@ -420,11 +420,6 @@ EXPORT_SYMBOL_GPL(spi_bitbang_init);
  * This routine registers the spi_controller, which will process requests in a
  * dedicated task, keeping IRQs unblocked most of the time.  To stop
  * processing those requests, call spi_bitbang_stop().
- *
- * On success, this routine will take a reference to the controller. The caller
- * is responsible for calling spi_bitbang_stop() to decrement the reference and
- * spi_controller_put() as counterpart of spi_alloc_host() to prevent a memory
- * leak.
  */
 int spi_bitbang_start(struct spi_bitbang *bitbang)
 {
@@ -438,11 +433,7 @@ int spi_bitbang_start(struct spi_bitbang *bitbang)
        /* driver may get busy before register() returns, especially
         * if someone registered boardinfo for devices
         */
-       ret = spi_register_controller(spi_controller_get(ctlr));
-       if (ret)
-               spi_controller_put(ctlr);
-
-       return ret;
+       return spi_register_controller(ctlr);
 }
 EXPORT_SYMBOL_GPL(spi_bitbang_start);
 

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index b47637888c5c6f650e2f840748cf4e10ad96e377..9a85a3ce5652055ba846b7f1fc57623579d8e152 100644 (file)
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -1032,6 +1032,8 @@ void dw_spi_remove_controller(struct dw_spi *dws)
        dw_spi_shutdown_chip(dws);
 
        free_irq(dws->irq, dws->ctlr);
+
+       spi_controller_put(dws->ctlr);
 }
 EXPORT_SYMBOL_NS_GPL(dw_spi_remove_controller, "SPI_DW_CORE");
 

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 9f2a7b8163b1011949bad5f18d825cdfe2210250..019d05cdefe693e55b9ca5ab9286b369721bc0f4 100644 (file)
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -1715,6 +1715,8 @@ static void dspi_remove(struct platform_device *pdev)
        dspi_release_dma(dspi);
        if (dspi->irq)
                free_irq(dspi->irq, dspi);
+
+       spi_controller_put(dspi->ctlr);
 }
 
 static void dspi_shutdown(struct platform_device *pdev)

diff --git a/drivers/spi/spi-mpc52xx.c b/drivers/spi/spi-mpc52xx.c
index 04c2270cd2cf694dde6c05849f35f219cc754f0c..70d8e17e8c43130a2c9027de5fbabf12faae603c 100644 (file)
--- a/drivers/spi/spi-mpc52xx.c
+++ b/drivers/spi/spi-mpc52xx.c
@@ -520,7 +520,7 @@ static int mpc52xx_spi_probe(struct platform_device *op)
 
 static void mpc52xx_spi_remove(struct platform_device *op)
 {
-       struct spi_controller *host = spi_controller_get(platform_get_drvdata(op));
+       struct spi_controller *host = platform_get_drvdata(op);
        struct mpc52xx_spi *ms = spi_controller_get_devdata(host);
        int i;
 

diff --git a/drivers/spi/spi-topcliff-pch.c b/drivers/spi/spi-topcliff-pch.c
index 02ced638d8b47ec792411ea4b08b8195d937e55b..c5409ca7faef3fe7b8a8b98dea0e3464c18fdbc9 100644 (file)
--- a/drivers/spi/spi-topcliff-pch.c
+++ b/drivers/spi/spi-topcliff-pch.c
@@ -1406,8 +1406,6 @@ static void pch_spi_pd_remove(struct platform_device *plat_dev)
        dev_dbg(&plat_dev->dev, "%s:[ch%d] irq=%d\n",
                __func__, plat_dev->id, board_dat->pdev->irq);
 
-       spi_controller_get(data->host);
-
        spi_unregister_controller(data->host);
 
        /* check for any pending messages; no action is taken if the queue

diff --git a/drivers/spi/spi-xilinx.c b/drivers/spi/spi-xilinx.c
index 9f065d4e27d19adabb9f4992cb89bf8292bf1f2e..3aeef70caa96bee741a22c881193bd90df5660e1 100644 (file)
--- a/drivers/spi/spi-xilinx.c
+++ b/drivers/spi/spi-xilinx.c
@@ -515,8 +515,6 @@ static void xilinx_spi_remove(struct platform_device *pdev)
        xspi->write_fn(0, regs_base + XIPIF_V123B_IIER_OFFSET);
        /* Disable the global IPIF interrupt */
        xspi->write_fn(0, regs_base + XIPIF_V123B_DGIER_OFFSET);
-
-       spi_controller_put(xspi->bitbang.ctlr);
 }
 
 /* work with hotplug and coldplug */

diff --git a/drivers/spi/spi-xtensa-xtfpga.c b/drivers/spi/spi-xtensa-xtfpga.c
index 71f0f176cfd91f610d6db414b941aac9cad5154e..d47a1e548fce6bcc39ff782368a5467bf043bd38 100644 (file)
--- a/drivers/spi/spi-xtensa-xtfpga.c
+++ b/drivers/spi/spi-xtensa-xtfpga.c
@@ -122,7 +122,6 @@ static void xtfpga_spi_remove(struct platform_device *pdev)
        struct xtfpga_spi *xspi = spi_controller_get_devdata(host);
 
        spi_bitbang_stop(&xspi->bitbang);
-       spi_controller_put(host);
 }
 
 MODULE_ALIAS("platform:" XTFPGA_SPI_NAME);

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 5f57de24b9f76c9fca06fddf5ae94f241bea1e42..0576bd00d3ef2c789010f8d81b110ed9c3ea95ab 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3226,9 +3226,9 @@ extern struct class spi_target_class;     /* dummy */
  * This must be called from context that can sleep.
  *
  * The caller is responsible for assigning the bus number and initializing the
- * controller's methods before calling spi_register_controller(); and (after
- * errors adding the device) calling spi_controller_put() to prevent a memory
- * leak.
+ * controller's methods before calling spi_register_controller(); and calling
+ * spi_controller_put() to prevent a memory leak when done with the
+ * controller.
  *
  * Return: the SPI controller structure on success, else NULL.
  */
@@ -3312,8 +3312,6 @@ struct spi_controller *__devm_spi_alloc_controller(struct device *dev,
        if (ret)
                return NULL;
 
-       ctlr->devm_allocated = true;
-
        return ctlr;
 }
 EXPORT_SYMBOL_GPL(__devm_spi_alloc_controller);
@@ -3579,8 +3577,7 @@ static void devm_spi_unregister_controller(void *ctlr)
  * Context: can sleep
  *
  * Register a SPI device as with spi_register_controller() which will
- * automatically be unregistered (and freed unless it has been allocated using
- * devm_spi_alloc_host/target()).
+ * automatically be unregistered.
  *
  * Return: zero on success, else a negative error code.
  */
@@ -3593,19 +3590,7 @@ int devm_spi_register_controller(struct device *dev,
        if (ret)
                return ret;
 
-       /*
-        * Prevent controller from being freed by spi_unregister_controller()
-        * if devm_add_action_or_reset() fails for a non-devres allocated
-        * controller.
-        */
-       spi_controller_get(ctlr);
-
-       ret = devm_add_action_or_reset(dev, devm_spi_unregister_controller, ctlr);
-
-       if (ret == 0 || ctlr->devm_allocated)
-               spi_controller_put(ctlr);
-
-       return ret;
+       return devm_add_action_or_reset(dev, devm_spi_unregister_controller, ctlr);
 }
 EXPORT_SYMBOL_GPL(devm_spi_register_controller);
 
@@ -3624,9 +3609,6 @@ static int __unregister(struct device *dev, void *null)
  * only ones directly touching chip registers.
  *
  * This must be called from context that can sleep.
- *
- * Note that this function also drops a reference to the controller unless it
- * has been allocated using devm_spi_alloc_host/target().
  */
 void spi_unregister_controller(struct spi_controller *ctlr)
 {
@@ -3661,13 +3643,6 @@ void spi_unregister_controller(struct spi_controller *ctlr)
 
        if (IS_ENABLED(CONFIG_SPI_DYNAMIC))
                mutex_unlock(&ctlr->add_lock);
-
-       /*
-        * Release the last reference on the controller if its driver
-        * has not yet been converted to devm_spi_alloc_host/target().
-        */
-       if (!ctlr->devm_allocated)
-               put_device(&ctlr->dev);
 }
 EXPORT_SYMBOL_GPL(spi_unregister_controller);
 

diff --git a/drivers/staging/greybus/spilib.c b/drivers/staging/greybus/spilib.c
index 24e9c909fa0211b3e2efb37a91adde76980853bf..e4d1ae8308aa19112124f03f8b61d9bf8cc83db1 100644 (file)
--- a/drivers/staging/greybus/spilib.c
+++ b/drivers/staging/greybus/spilib.c
@@ -547,13 +547,10 @@ int gb_spilib_master_init(struct gb_connection *connection, struct device *dev,
 
        return 0;
 
-exit_spi_put:
-       spi_controller_put(ctlr);
-
-       return ret;
-
 exit_spi_unregister:
        spi_unregister_controller(ctlr);
+exit_spi_put:
+       spi_controller_put(ctlr);
 
        return ret;
 }
@@ -564,6 +561,7 @@ void gb_spilib_master_exit(struct gb_connection *connection)
        struct spi_controller *ctlr = gb_connection_get_data(connection);
 
        spi_unregister_controller(ctlr);
+       spi_controller_put(ctlr);
 }
 EXPORT_SYMBOL_GPL(gb_spilib_master_exit);
 

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 79513f5941cca1d15a06e6a3aacef0615a160068..f6ed93eff00bf7c9a22c8f319b00951a0d7b6790 100644 (file)
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -424,7 +424,6 @@ extern struct spi_device *devm_spi_new_ancillary_device(struct spi_device *spi,
  * @flags: other constraints relevant to this driver
  * @slave: indicates that this is an SPI slave controller
  * @target: indicates that this is an SPI target controller
- * @devm_allocated: whether the allocation of this struct is devres-managed
  * @max_transfer_size: function that returns the max transfer size for
  *     a &spi_device; may be %NULL, so the default %SIZE_MAX will be used.
  * @max_message_size: function that returns the max message size for
@@ -629,9 +628,6 @@ struct spi_controller {
         */
 #define SPI_CONTROLLER_MULTI_CS                BIT(7)
 
-       /* Flag indicating if the allocation of this struct is devres-managed */
-       bool                    devm_allocated;
-
        union {
                /* Flag indicating this is an SPI slave controller */
                bool                    slave;