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.

Convert the platform driver to use new helper and make the driver_override field const char (it is not modified by the core).

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/base/driver.c | 56 +++++++++++++++++++++++++++++++++ drivers/base/platform.c | 28 +++-------------- include/linux/device/driver.h | 2 ++ include/linux/platform_device.h | 6 +++- 4 files changed, 67 insertions(+), 25 deletions(-)

diff --git a/drivers/base/driver.c b/drivers/base/driver.c index 8c0d33e182fd..ba2510117484 100644 --- a/drivers/base/driver.c +++ b/drivers/base/driver.c @@ -30,6 +30,62 @@ static struct device *next_device(struct klist_iter *i) return dev; }

+/** + * driver_set_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: NUL terminated string, new driver name to force a match, pass empty + * string to clear it + * @len: length of @s + * + * Helper to set 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, const char **override, + const char *s, size_t len) +{ + const char *new, *old; + char *cp; + + if (!dev || !override || !s) + return -EINVAL; + + /* + * The stored value will be used in sysfs show callback (sysfs_emit()), + * which has a length limit of PAGE_SIZE and adds a trailing newline. + * Thus we can store one character less to avoid truncation during sysfs + * show. + */ + if (len >= (PAGE_SIZE - 1)) + return -EINVAL; + + new = kstrndup(s, len, GFP_KERNEL); + if (!new) + return -ENOMEM; + + cp = strchr(new, '\n'); + if (cp) + *cp = '\0'; + + device_lock(dev); + old = *override; + if (cp != 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 8cc272fd5c99..b684157b7f2f 100644 --- a/drivers/base/platform.c +++ b/drivers/base/platform.c @@ -1275,31 +1275,11 @@ 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; - - /* 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); + int ret;

- kfree(old); + ret = driver_set_override(dev, &pdev->driver_override, buf, count); + if (ret) + return ret;

return count; } diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h index 15e7c5e15d62..700453017e1c 100644 --- a/include/linux/device/driver.h +++ b/include/linux/device/driver.h @@ -151,6 +151,8 @@ 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, const char **override, + const char *s, size_t len); 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..582d83ed9a91 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. Do not set directly, because core + * frees it. Use driver_set_override() to set or clear it. + */ + const char *driver_override;

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

Use a helper to set driver_override to reduce amount of duplicated code. Make the driver_override field const char, because it is not modified by the core and it matches other subsystems.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/bus/fsl-mc/fsl-mc-bus.c | 25 ++++--------------------- include/linux/fsl/mc.h | 6 ++++-- 2 files changed, 8 insertions(+), 23 deletions(-)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c index 8fd4a356a86e..ba01c7f4de92 100644 --- a/drivers/bus/fsl-mc/fsl-mc-bus.c +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c @@ -166,31 +166,14 @@ static ssize_t driver_override_store(struct device *dev, const char *buf, size_t count) { struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev); - char *driver_override, *old = mc_dev->driver_override; - char *cp; + int ret;

if (WARN_ON(dev->bus != &fsl_mc_bus_type)) return -EINVAL;

- 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'; - - if (strlen(driver_override)) { - mc_dev->driver_override = driver_override; - } else { - kfree(driver_override); - mc_dev->driver_override = NULL; - } - - kfree(old); + ret = driver_set_override(dev, &mc_dev->driver_override, buf, count); + if (ret) + return ret;

return count; } diff --git a/include/linux/fsl/mc.h b/include/linux/fsl/mc.h index 7b6c42bfb660..7a87ab9eba99 100644 --- a/include/linux/fsl/mc.h +++ b/include/linux/fsl/mc.h @@ -170,7 +170,9 @@ struct fsl_mc_obj_desc { * @regions: pointer to array of MMIO region entries * @irqs: pointer to array of pointers to interrupts allocated to this device * @resource: generic resource associated with this MC object device, if any. - * @driver_override: driver name to force a match + * @driver_override: driver name to force a match; do not set directly, + * because core frees it; use driver_set_override() to + * set or clear it. * * Generic device object for MC object devices that are "attached" to a * MC bus. @@ -204,7 +206,7 @@ struct fsl_mc_device { struct fsl_mc_device_irq **irqs; struct fsl_mc_resource *resource; struct device_link *consumer_link; - char *driver_override; + const char *driver_override; };

#define to_fsl_mc_device(_dev) \

Use a helper to set driver_override to reduce amount of duplicated code. Make the driver_override field const char, because it is not modified by the core and it matches other subsystems.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com Acked-by: Bjorn Helgaas bhelgaas@google.com --- drivers/pci/pci-sysfs.c | 28 ++++------------------------ include/linux/pci.h | 6 +++++- 2 files changed, 9 insertions(+), 25 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 602f0fb0b007..5c42965c32c2 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -567,31 +567,11 @@ static ssize_t driver_override_store(struct device *dev, const char *buf, size_t count) { struct pci_dev *pdev = to_pci_dev(dev); - char *driver_override, *old, *cp; - - /* 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); + int ret;

- kfree(old); + ret = driver_set_override(dev, &pdev->driver_override, buf, count); + if (ret) + return ret;

return count; } diff --git a/include/linux/pci.h b/include/linux/pci.h index 60d423d8f0c4..415491fb85f4 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -516,7 +516,11 @@ struct pci_dev { u16 acs_cap; /* ACS Capability offset */ phys_addr_t rom; /* Physical address if not from BAR */ size_t romlen; /* Length if not from BAR */ - char *driver_override; /* Driver name to force a match */ + /* + * Driver name to force a match. Do not set directly, because core + * frees it. Use driver_set_override() to set or clear it. + */ + const char *driver_override;

unsigned long priv_flags; /* Private flags for the PCI driver */

Use a helper to set driver_override to reduce amount of duplicated code. Make the driver_override field const char, because it is not modified by the core and it matches other subsystems.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com Acked-by: Vineeth Vijayan vneethv@linux.ibm.com --- drivers/s390/cio/cio.h | 6 +++++- drivers/s390/cio/css.c | 28 ++++------------------------ 2 files changed, 9 insertions(+), 25 deletions(-)

diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h index 1cb9daf9c645..fa8df50bb49e 100644 --- a/drivers/s390/cio/cio.h +++ b/drivers/s390/cio/cio.h @@ -103,7 +103,11 @@ struct subchannel { struct work_struct todo_work; struct schib_config config; u64 dma_mask; - char *driver_override; /* Driver name to force a match */ + /* + * Driver name to force a match. Do not set directly, because core + * frees it. Use driver_set_override() to set or clear it. + */ + const char *driver_override; } __attribute__ ((aligned(8)));

DECLARE_PER_CPU_ALIGNED(struct irb, cio_irb); diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c index fa8293335077..913b6ddd040b 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -338,31 +338,11 @@ static ssize_t driver_override_store(struct device *dev, const char *buf, size_t count) { struct subchannel *sch = to_subchannel(dev); - char *driver_override, *old, *cp; - - /* 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 = sch->driver_override; - if (strlen(driver_override)) { - sch->driver_override = driver_override; - } else { - kfree(driver_override); - sch->driver_override = NULL; - } - device_unlock(dev); + int ret;

- kfree(old); + ret = driver_set_override(dev, &sch->driver_override, buf, count); + if (ret) + return ret;

return count; }

Use a helper to set driver_override to reduce amount of duplicated code.

Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/vdpa/vdpa.c | 29 ++++------------------------- include/linux/vdpa.h | 4 +++- 2 files changed, 7 insertions(+), 26 deletions(-)

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c index 1ea525433a5c..2dabed1df35c 100644 --- a/drivers/vdpa/vdpa.c +++ b/drivers/vdpa/vdpa.c @@ -77,32 +77,11 @@ static ssize_t driver_override_store(struct device *dev, const char *buf, size_t count) { struct vdpa_device *vdev = dev_to_vdpa(dev); - const char *driver_override, *old; - char *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 = vdev->driver_override; - if (strlen(driver_override)) { - vdev->driver_override = driver_override; - } else { - kfree(driver_override); - vdev->driver_override = NULL; - } - device_unlock(dev); - - kfree(old); + ret = driver_set_override(dev, &vdev->driver_override, buf, count); + if (ret) + return ret;

return count; } diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h index 721089bb4c84..37117404660e 100644 --- a/include/linux/vdpa.h +++ b/include/linux/vdpa.h @@ -64,7 +64,9 @@ struct vdpa_mgmt_dev; * struct vdpa_device - representation of a vDPA device * @dev: underlying device * @dma_dev: the actual device that is performing DMA - * @driver_override: driver name to force a match + * @driver_override: driver name to force a match; do not set directly, + * because core frees it; use driver_set_override() to + * set or clear it. * @config: the configuration ops for this device. * @cf_mutex: Protects get and set access to configuration layout. * @index: device index

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: 950a7388f02b ("rpmsg: Turn name service into a stand alone driver") Fixes: c0cdc19f84a4 ("rpmsg: Driver for user space endpoint interface") Cc: stable@vger.kernel.org Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com --- drivers/rpmsg/rpmsg_core.c | 3 ++- drivers/rpmsg/rpmsg_internal.h | 13 +++++++++++-- drivers/rpmsg/rpmsg_ns.c | 14 ++++++++++++-- include/linux/rpmsg.h | 6 ++++-- 4 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c index d9e612f4f0f2..6e2bf2742973 100644 --- a/drivers/rpmsg/rpmsg_core.c +++ b/drivers/rpmsg/rpmsg_core.c @@ -397,7 +397,8 @@ field##_store(struct device *dev, struct device_attribute *attr, \ const char *buf, size_t sz) \ { \ struct rpmsg_device *rpdev = to_rpmsg_device(dev); \ - char *new, *old; \ + const char *old; \ + char *new; \ \ new = kstrndup(buf, sz, GFP_KERNEL); \ if (!new) \ diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h index b1245d3ed7c6..31345d6e9a7e 100644 --- a/drivers/rpmsg/rpmsg_internal.h +++ b/drivers/rpmsg/rpmsg_internal.h @@ -92,10 +92,19 @@ int rpmsg_release_channel(struct rpmsg_device *rpdev, */ static inline int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev) { + int ret; + strcpy(rpdev->id.name, "rpmsg_chrdev"); - rpdev->driver_override = "rpmsg_chrdev"; + ret = driver_set_override(&rpdev->dev, &rpdev->driver_override, + "rpmsg_chrdev", strlen("rpmsg_chrdev")); + if (ret) + return ret; + + ret = rpmsg_register_device(rpdev); + if (ret) + kfree(rpdev->driver_override);

- return rpmsg_register_device(rpdev); + return ret; }

#endif diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c index 762ff1ae279f..95a51543f5ad 100644 --- a/drivers/rpmsg/rpmsg_ns.c +++ b/drivers/rpmsg/rpmsg_ns.c @@ -20,12 +20,22 @@ */ int rpmsg_ns_register_device(struct rpmsg_device *rpdev) { + int ret; + strcpy(rpdev->id.name, "rpmsg_ns"); - rpdev->driver_override = "rpmsg_ns"; + ret = driver_set_override(&rpdev->dev, &rpdev->driver_override, + "rpmsg_ns", strlen("rpmsg_ns")); + if (ret) + return ret; + rpdev->src = RPMSG_NS_ADDR; rpdev->dst = RPMSG_NS_ADDR;

- return rpmsg_register_device(rpdev); + ret = rpmsg_register_device(rpdev); + if (ret) + kfree(rpdev->driver_override); + + return ret; } EXPORT_SYMBOL(rpmsg_ns_register_device);

diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h index 02fa9116cd60..20c8cd1cde21 100644 --- a/include/linux/rpmsg.h +++ b/include/linux/rpmsg.h @@ -41,7 +41,9 @@ struct rpmsg_channel_info { * rpmsg_device - device that belong to the rpmsg bus * @dev: the device struct * @id: device id (used to match between rpmsg drivers and devices) - * @driver_override: driver name to force a match + * @driver_override: driver name to force a match; do not set directly, + * because core frees it; use driver_set_override() to + * set or clear it. * @src: local address * @dst: destination address * @ept: the rpmsg endpoint of this channel @@ -51,7 +53,7 @@ struct rpmsg_channel_info { struct rpmsg_device { struct device dev; struct rpmsg_device_id id; - char *driver_override; + const char *driver_override; u32 src; u32 dst; struct rpmsg_endpoint *ept;