Messages in this thread Patch in this message | | | Date | Fri, 4 Dec 2009 11:06:57 -0500 (EST) | From | Alan Stern <> | Subject | [PATCH] Driver core: fix race in dev_driver_string |
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This patch (as1310) works around a race in dev_driver_string(). If the device is unbound while the function is running, dev->driver might become NULL after we test it and before we dereference it.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: stable@kernel.org
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Oliver:
We don't have to worry about the device structure being deallocated while the routine is running. If that happens it's a bug in the caller: improper refcounting.
Alan Stern
Index: usb-2.6/drivers/base/core.c =================================================================== --- usb-2.6.orig/drivers/base/core.c +++ usb-2.6/drivers/base/core.c @@ -56,7 +56,14 @@ static inline int device_is_not_partitio */ const char *dev_driver_string(const struct device *dev) { - return dev->driver ? dev->driver->name : + struct device_driver *drv; + + /* dev->driver can change to NULL underneath us because of unbinding, + * so be careful about accessing it. dev->bus and dev->class should + * never change once they are set, so they don't need special care. + */ + drv = ACCESS_ONCE(dev->driver); + return drv ? drv->name : (dev->bus ? dev->bus->name : (dev->class ? dev->class->name : "")); }
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