From: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org
commit 6c2f421174273de8f83cde4286d1c076d43a2d35 upstream.
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)
Provide a helper which clearly documents the usage of driver_override. This will allow later to reuse the helper and reduce the amount of duplicated code.
Convert the platform driver to use a new helper and make the driver_override field const char (it is not modified by the core).
Reviewed-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Acked-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Link: https://lore.kernel.org/r/20220419113435.246203-2-krzysztof.kozlowski@linaro... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Lee Jones lee@kernel.org --- drivers/base/driver.c | 69 +++++++++++++++++++++++++++++++++ drivers/base/platform.c | 28 ++----------- include/linux/device/driver.h | 2 + include/linux/platform_device.h | 6 ++- 4 files changed, 80 insertions(+), 25 deletions(-)
diff --git a/drivers/base/driver.c b/drivers/base/driver.c index 8c0d33e182fd5..1b9d47b10bd0a 100644 --- a/drivers/base/driver.c +++ b/drivers/base/driver.c @@ -30,6 +30,75 @@ 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 ("" or "\n", where the latter is only for sysfs + * interface). + * @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 (!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; + + if (!len) { + /* Empty string passed - clear override */ + device_lock(dev); + old = *override; + *override = NULL; + device_unlock(dev); + kfree(old); + + return 0; + } + + cp = strnchr(s, len, '\n'); + if (cp) + len = cp - s; + + new = kstrndup(s, len, GFP_KERNEL); + if (!new) + return -ENOMEM; + + device_lock(dev); + old = *override; + if (cp != s) { + *override = new; + } else { + /* "\n" passed - clear override */ + 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 88aef93eb4ddf..647066229fec3 100644 --- a/drivers/base/platform.c +++ b/drivers/base/platform.c @@ -1046,31 +1046,11 @@ 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 ee7ba5b5417e5..a44f5adeaef5a 100644 --- a/include/linux/device/driver.h +++ b/include/linux/device/driver.h @@ -150,6 +150,8 @@ 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 17f9cd5626c83..e7a83b0218077 100644 --- a/include/linux/platform_device.h +++ b/include/linux/platform_device.h @@ -30,7 +30,11 @@ 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;
From: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org
commit e5f89131a06142e91073b6959d91cea73861d40e upstream.
Memory pointed by variable 'old' in field store macro is not modified, so it can be made a pointer to const.
Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Link: https://lore.kernel.org/r/20220419113435.246203-12-krzysztof.kozlowski@linar... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Lee Jones lee@kernel.org --- drivers/rpmsg/rpmsg_core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c index 028ca5961bc2a..ef32fd66e8c2d 100644 --- a/drivers/rpmsg/rpmsg_core.c +++ b/drivers/rpmsg/rpmsg_core.c @@ -332,7 +332,8 @@ 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) \
From: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org
commit 42cd402b8fd4672b692400fe5f9eecd55d2794ac upstream.
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") Reviewed-by: Bjorn Andersson bjorn.andersson@linaro.org Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Link: https://lore.kernel.org/r/20220419113435.246203-13-krzysztof.kozlowski@linar... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Lee Jones lee@kernel.org --- drivers/rpmsg/rpmsg_internal.h | 13 +++++++++++-- include/linux/rpmsg.h | 6 ++++-- 2 files changed, 15 insertions(+), 4 deletions(-)
diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h index 3fc83cd50e98f..9165e3c811be4 100644 --- a/drivers/rpmsg/rpmsg_internal.h +++ b/drivers/rpmsg/rpmsg_internal.h @@ -84,10 +84,19 @@ struct device *rpmsg_find_device(struct device *parent, */ 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, + rpdev->id.name, strlen(rpdev->id.name)); + 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/include/linux/rpmsg.h b/include/linux/rpmsg.h index a68972b097b72..6e7690e20dc51 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 @@ -50,7 +52,7 @@ 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;
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