Several core drivers and buses expect that driver_override is a dynamically allocated memory thus later they can kfree() it.

However such assumption is not documented, there were in the past and there are already users setting it to a string literal. This leads to kfree() of static memory during device release (e.g. in error paths or during unbind):

kernel BUG at ../mm/slub.c:3960! Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM ... (kfree) from [<c058da50>] (platform_device_release+0x88/0xb4) (platform_device_release) from [<c0585be0>] (device_release+0x2c/0x90) (device_release) from [<c0a69050>] (kobject_put+0xec/0x20c) (kobject_put) from [<c0f2f120>] (exynos5_clk_probe+0x154/0x18c) (exynos5_clk_probe) from [<c058de70>] (platform_drv_probe+0x6c/0xa4) (platform_drv_probe) from [<c058b7ac>] (really_probe+0x280/0x414) (really_probe) from [<c058baf4>] (driver_probe_device+0x78/0x1c4) (driver_probe_device) from [<c0589854>] (bus_for_each_drv+0x74/0xb8) (bus_for_each_drv) from [<c058b48c>] (__device_attach+0xd4/0x16c) (__device_attach) from [<c058a638>] (bus_probe_device+0x88/0x90) (bus_probe_device) from [<c05871fc>] (device_add+0x3dc/0x62c) (device_add) from [<c075ff10>] (of_platform_device_create_pdata+0x94/0xbc) (of_platform_device_create_pdata) from [<c07600ec>] (of_platform_bus_create+0x1a8/0x4fc) (of_platform_bus_create) from [<c0760150>] (of_platform_bus_create+0x20c/0x4fc) (of_platform_bus_create) from [<c07605f0>] (of_platform_populate+0x84/0x118) (of_platform_populate) from [<c0f3c964>] (of_platform_default_populate_init+0xa0/0xb8) (of_platform_default_populate_init) from [<c01031f8>] (do_one_initcall+0x8c/0x404) (do_one_initcall) from [<c0f012c0>] (kernel_init_freeable+0x3d0/0x4d8) (kernel_init_freeable) from [<c0a7def0>] (kernel_init+0x8/0x114) (kernel_init) from [<c01010b4>] (ret_from_fork+0x14/0x20)

Provide a helper which clearly documents the usage of driver_override. This will allow later to reuse the helper and reduce amount of duplicated code.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/base/driver.c | 44 +++++++++++++++++++++++++++++++++ drivers/base/platform.c | 24 +++--------------- include/linux/device/driver.h | 1 + include/linux/platform_device.h | 6 ++++- 4 files changed, 54 insertions(+), 21 deletions(-)

diff --git a/drivers/base/driver.c b/drivers/base/driver.c index 8c0d33e182fd..79efe51bb4c0 100644 --- a/drivers/base/driver.c +++ b/drivers/base/driver.c @@ -30,6 +30,50 @@ static struct device *next_device(struct klist_iter *i) return dev; }

+/* + * set_driver_override() - Helper to set or clear driver override. + * @dev: Device to change + * @override: Address of string to change (e.g. &device->driver_override); + * The contents will be freed and hold newly allocated override. + * @s: NULL terminated string, new driver name to force a match, pass empty + * string to clear it + * + * Helper to setr or clear driver override in a device, intended for the cases + * when the driver_override field is allocated by driver/bus code. + * + * Returns: 0 on success or a negative error code on failure. + */ +int driver_set_override(struct device *dev, char **override, const char *s) +{ + char *new, *old, *cp; + + if (!dev || !override || !s) + return -EINVAL; + + new = kstrndup(s, strlen(s), GFP_KERNEL); + if (!new) + return -ENOMEM; + + cp = strchr(new, '\n'); + if (cp) + *cp = '\0'; + + device_lock(dev); + old = *override; + if (strlen(new)) { + *override = new; + } else { + kfree(new); + *override = NULL; + } + device_unlock(dev); + + kfree(old); + + return 0; +} +EXPORT_SYMBOL_GPL(driver_set_override); + /** * driver_for_each_device - Iterator for devices bound to a driver. * @drv: Driver we're iterating. diff --git a/drivers/base/platform.c b/drivers/base/platform.c index 6cb04ac48bf0..d8853b32ea10 100644 --- a/drivers/base/platform.c +++ b/drivers/base/platform.c @@ -1275,31 +1275,15 @@ static ssize_t driver_override_store(struct device *dev, const char *buf, size_t count) { struct platform_device *pdev = to_platform_device(dev); - char *driver_override, *old, *cp; + int ret;

/* We need to keep extra room for a newline */ if (count >= (PAGE_SIZE - 1)) return -EINVAL;

- driver_override = kstrndup(buf, count, GFP_KERNEL); - if (!driver_override) - return -ENOMEM; - - cp = strchr(driver_override, '\n'); - if (cp) - *cp = '\0'; - - device_lock(dev); - old = pdev->driver_override; - if (strlen(driver_override)) { - pdev->driver_override = driver_override; - } else { - kfree(driver_override); - pdev->driver_override = NULL; - } - device_unlock(dev); - - kfree(old); + ret = driver_set_override(dev, &pdev->driver_override, buf); + if (ret) + return ret;

return count; } diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h index 15e7c5e15d62..81c0d9f65a40 100644 --- a/include/linux/device/driver.h +++ b/include/linux/device/driver.h @@ -151,6 +151,7 @@ extern int __must_check driver_create_file(struct device_driver *driver, extern void driver_remove_file(struct device_driver *driver, const struct driver_attribute *attr);

+int driver_set_override(struct device *dev, char **override, const char *s); extern int __must_check driver_for_each_device(struct device_driver *drv, struct device *start, void *data, diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h index 7c96f169d274..37ac14459499 100644 --- a/include/linux/platform_device.h +++ b/include/linux/platform_device.h @@ -31,7 +31,11 @@ struct platform_device { struct resource *resource;

const struct platform_device_id *id_entry; - char *driver_override; /* Driver name to force a match */ + /* + * Driver name to force a match, use + * driver_set_override() to set or clear it. + */ + char *driver_override;

/* MFD cell pointer */ struct mfd_cell *mfd_cell;

Use a helper for seting driver_override to reduce amount of duplicated code.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/amba/bus.c | 24 ++++-------------------- 1 file changed, 4 insertions(+), 20 deletions(-)

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c index e1a5eca3ae3c..12410c05ec70 100644 --- a/drivers/amba/bus.c +++ b/drivers/amba/bus.c @@ -94,31 +94,15 @@ static ssize_t driver_override_store(struct device *_dev, const char *buf, size_t count) { struct amba_device *dev = to_amba_device(_dev); - char *driver_override, *old, *cp; + int ret;

/* We need to keep extra room for a newline */ if (count >= (PAGE_SIZE - 1)) return -EINVAL;

- driver_override = kstrndup(buf, count, GFP_KERNEL); - if (!driver_override) - return -ENOMEM; - - cp = strchr(driver_override, '\n'); - if (cp) - *cp = '\0'; - - device_lock(_dev); - old = dev->driver_override; - if (strlen(driver_override)) { - dev->driver_override = driver_override; - } else { - kfree(driver_override); - dev->driver_override = NULL; - } - device_unlock(_dev); - - kfree(old); + ret = driver_set_override(_dev, &dev->driver_override, buf); + if (ret) + return ret;

return count; }

Use a helper for seting driver_override to reduce amount of duplicated code.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/hv/vmbus_drv.c | 24 ++++-------------------- 1 file changed, 4 insertions(+), 20 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 12a2b37e87f3..f2435cc8b680 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -575,31 +575,15 @@ static ssize_t driver_override_store(struct device *dev, const char *buf, size_t count) { struct hv_device *hv_dev = device_to_hv_device(dev); - char *driver_override, *old, *cp; + int ret;

/* We need to keep extra room for a newline */ if (count >= (PAGE_SIZE - 1)) return -EINVAL;

- driver_override = kstrndup(buf, count, GFP_KERNEL); - if (!driver_override) - return -ENOMEM; - - cp = strchr(driver_override, '\n'); - if (cp) - *cp = '\0'; - - device_lock(dev); - old = hv_dev->driver_override; - if (strlen(driver_override)) { - hv_dev->driver_override = driver_override; - } else { - kfree(driver_override); - hv_dev->driver_override = NULL; - } - device_unlock(dev); - - kfree(old); + ret = driver_set_override(dev, &hv_dev->driver_override, buf); + if (ret) + return ret;

return count; }

Use a helper for seting driver_override to reduce amount of duplicated code.

Remove also "const" from the definition of spi_device.driver_override, because it is not correct. The SPI driver already treats it as dynamic, not const, memory.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/spi/spi.c | 20 ++++---------------- include/linux/spi/spi.h | 2 +- 2 files changed, 5 insertions(+), 17 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 4599b121d744..0c7e2c34f4a3 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -74,27 +74,15 @@ static ssize_t driver_override_store(struct device *dev, struct spi_device *spi = to_spi_device(dev); const char *end = memchr(buf, '\n', count); const size_t len = end ? end - buf : count; - const char *driver_override, *old; + int ret;

/* We need to keep extra room for a newline when displaying value */ if (len >= (PAGE_SIZE - 1)) return -EINVAL;

- driver_override = kstrndup(buf, len, GFP_KERNEL); - if (!driver_override) - return -ENOMEM; - - device_lock(dev); - old = spi->driver_override; - if (len) { - spi->driver_override = driver_override; - } else { - /* Empty string, disable driver override */ - spi->driver_override = NULL; - kfree(driver_override); - } - device_unlock(dev); - kfree(old); + ret = driver_set_override(dev, &spi->driver_override, buf); + if (ret) + return ret;

return count; } diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 7ab3fed7b804..01224d07aaff 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -184,7 +184,7 @@ struct spi_device { void *controller_state; void *controller_data; char modalias[SPI_NAME_SIZE]; - const char *driver_override; + char *driver_override; int cs_gpio; /* LEGACY: chip select gpio */ struct gpio_desc *cs_gpiod; /* chip select gpio desc */ struct spi_delay word_delay; /* inter-word delay */

The driver_override field from platform driver should not be initialized from static memory (string literal) because the core later kfree() it, for example when driver_override is set via sysfs.

Use dedicated helper to set driver_override properly.

Fixes: 77d8f3068c63 ("clk: imx: scu: add two cells binding support") Cc: stable@vger.kernel.org Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/clk/imx/clk-scu.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-scu.c b/drivers/clk/imx/clk-scu.c index 083da31dc3ea..15e1d670e51f 100644 --- a/drivers/clk/imx/clk-scu.c +++ b/drivers/clk/imx/clk-scu.c @@ -683,7 +683,12 @@ struct clk_hw *imx_clk_scu_alloc_dev(const char *name, return ERR_PTR(ret); }

- pdev->driver_override = "imx-scu-clk"; + ret = driver_set_override(&pdev->dev, &pdev->driver_override, + "imx-scu-clk"); + if (ret) { + platform_device_put(pdev); + return ret; + }

ret = imx_clk_scu_attach_pd(&pdev->dev, rsrc_id); if (ret)

The driver_override field from platform driver should not be initialized from static memory (string literal) because the core later kfree() it, for example when driver_override is set via sysfs.

Use dedicated helper to set driver_override properly.

Fixes: 917809e2280b ("slimbus: ngd: Add qcom SLIMBus NGD driver") Cc: stable@vger.kernel.org Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/slimbus/qcom-ngd-ctrl.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/slimbus/qcom-ngd-ctrl.c b/drivers/slimbus/qcom-ngd-ctrl.c index 7040293c2ee8..e1a8de4d41fb 100644 --- a/drivers/slimbus/qcom-ngd-ctrl.c +++ b/drivers/slimbus/qcom-ngd-ctrl.c @@ -1434,6 +1434,7 @@ static int of_qcom_slim_ngd_register(struct device *parent, const struct of_device_id *match; struct device_node *node; u32 id; + int ret;

match = of_match_node(qcom_slim_ngd_dt_match, parent->of_node); data = match->data; @@ -1455,7 +1456,16 @@ static int of_qcom_slim_ngd_register(struct device *parent, } ngd->id = id; ngd->pdev->dev.parent = parent; - ngd->pdev->driver_override = QCOM_SLIM_NGD_DRV_NAME; + + ret = driver_set_override(&ngd->pdev->dev, + &ngd->pdev->driver_override, + QCOM_SLIM_NGD_DRV_NAME); + if (ret) { + platform_device_put(ngd->pdev); + kfree(ngd); + of_node_put(node); + return ret; + } ngd->pdev->dev.of_node = node; ctrl->ngd = ngd;