Messages in this thread Patch in this message | | | From | Stepan Moskovchenko <> | Subject | [PATCH] of: Deep-copy names of platform devices | Date | Tue, 12 Aug 2014 17:57:24 -0700 |
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When we parse the device tree and allocate platform devices, the 'name' of the newly-created platform_device is set to point to the 'name' field of the 'struct device' embedded within the platform_device. This is dangerous, because the name of the 'struct device' is dynamically allocated. Drivers may call dev_set_name() on the device, which will free and reallocate the name of the device, leaving the 'name' of the platform_device pointing to the now-freed memory.
Furthermore, if the dev_set_name() call is made from a driver's probe() function and a subsequent request results in probe deferral, the dangling 'name' reference may lead to the device being re-probed using the wrong driver.
To mitigate these scenarios, we use kstrdup to perform a deep copy of the device name when assigning the name of the platform_device, so that the platform_device name is unaffected by any calls to dev_set_name() that might made by drivers to rename the embedded 'struct device'.
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org> --- This is technically a 'v2' patch, but it looks like I used an old version of MAINTAINERS, so I'll just re-send this as a new patch to avoid confusion for people who missed the original.
I suppose creating a 'pdev_set_name' API may seem like another possibility, but I feel that dev.name and pdev.name have two different meanings. One is used for device/driver binding purposes, whereas the other serves a more general identification purpose, and is used for things like sysfs. Drivers might want to change dev.name while leaving the pdev.name alone. I guess yet another possibility would be to prohibit calling dev_set_name() on devices created from device tree, but a driver does not necessarily know how a given platform_device was allocated.
Steve
drivers/of/device.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/of/device.c b/drivers/of/device.c index f685e55..3e116f6 100644 --- a/drivers/of/device.c +++ b/drivers/of/device.c @@ -54,7 +54,7 @@ int of_device_add(struct platform_device *ofdev)
/* name and id have to be set so that the platform bus doesn't get * confused on matching */ - ofdev->name = dev_name(&ofdev->dev); + ofdev->name = kstrdup(dev_name(&ofdev->dev), GFP_KERNEL); ofdev->id = -1;
/* device_add will assume that this device is on the same node as @@ -76,6 +76,7 @@ EXPORT_SYMBOL(of_device_register); void of_device_unregister(struct platform_device *ofdev) { device_unregister(&ofdev->dev); + kfree(ofdev->name); } EXPORT_SYMBOL(of_device_unregister);
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