The core platform driver expects that driver_override is an dynamically
allocated memory so later it can kfree() it.
However such assumption is not documented and there are already users
setting it to a const memory. This leads to kfree() of const 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.
Signed-off-by: Krzysztof Kozlowski <k...@kernel.org>
---
drivers/base/platform.c | 63 ++++++++++++++++++++++++++++-------------
include/linux/platform_device.h | 9 +++++-
2 files changed, 51 insertions(+), 21 deletions(-)
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 0d3611cd1b3b..1458903a33c8 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -730,6 +730,45 @@ int __init_or_module __platform_driver_probe(struct
platform_driver *drv,
}
EXPORT_SYMBOL_GPL(__platform_driver_probe);
+/*
+ * platform_set_driver_override() - Helper to set or clear driver override.
+ * @pdev: platform device
+ * @override: Driver name to force a match, pass empty string to clear it
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int platform_set_driver_override(struct platform_device *pdev,
+ const char *override)
+{
+ struct device *dev = &pdev->dev;
+ char *driver_override, *old, *cp;
+
+ if (!pdev || !override)
+ return -EINVAL;
+
+ driver_override = kstrndup(override, strlen(override), 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);
+
+ return 0;
+}
+
/**
* __platform_create_bundle - register driver and create corresponding device
* @driver: platform driver structure
@@ -879,31 +918,15 @@ 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 = platform_set_driver_override(pdev, buf);
+ if (ret)
+ return ret;
return count;
}
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index c7c081dc6034..1dd06fed3306 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -29,7 +29,11 @@ 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
+ * platform_set_driver_override() to set or clear it.
+ */
+ char *driver_override;
/* MFD cell pointer */
struct mfd_cell *mfd_cell;
@@ -220,6 +224,9 @@ static inline void platform_set_drvdata(struct
platform_device *pdev,
dev_set_drvdata(&pdev->dev, data);
}
+int platform_set_driver_override(struct platform_device *pdev,
+ const char *override);
+
/* module_platform_driver() - Helper macro for drivers that don't do
* anything special in module init/exit. This eliminates a lot of
* boilerplate. Each module may only use this macro once, and
--
2.7.4
