On Fri, Jul 19, 2013 at 7:17 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 18 Jul 2013, Luis R. Rodriguez wrote: > >> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxxxxxxxx> >> >> The Linux kernel had tons of code which at times cleared the >> drvdata upon probe failure or release. There are however a bunch >> of drivers that didn't clear this. >> >> Commit 0998d063 implmented clearing this upon device_release_driver() >> and dealt with probe failure on driver_probe_device(). After this the >> kernel was cleaned up separately with *tons* of patches to remove all >> these driver specific settings given that the clearing is now done >> internally by the device core. >> >> Instead of ifdef'ing code back in for older code where it was properly >> in place backport this by piggy backing the new required code upon the >> calls used in place. There is a small race here upon device_release_driver() >> but we can live with that theoretical race. >> >> Due to the way we hack this backport we can't use a separate namespace >> as we have with other symbols. >> >> mcgrof@frijol ~/linux-stable (git::master)$ git describe --contains \ >> 0998d0631001288a5974afc0b2a5f568bcdecb4d >> v3.6-rc1~99^2~14^2~17 >> >> commit 0998d0631001288a5974afc0b2a5f568bcdecb4d >> Author: Hans de Goede <hdegoede@xxxxxxxxxx> >> Date: Wed May 23 00:09:34 2012 +0200 >> >> device-core: Ensure drvdata = NULL when no driver is bound >> >> 1) drvdata is for a driver to store a pointer to driver specific data >> 2) If no driver is bound, there is no driver specific data associated with >> the device >> 3) Thus logically drvdata should be NULL if no driver is bound. >> >> But many drivers don't clear drvdata on device_release, or set drvdata >> early on in probe and leave it set on probe error. Both of which results >> in a dangling pointer in drvdata. >> >> This patch enforce for drvdata to be NULL after device_release or on probe >> failure. >> >> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> >> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > This is not a very good idea. Although setting drvdata to NULL allowed > a lot of code to be removed, it also exposed a bunch of hidden bugs -- > drivers were using the drvdata value even after their remove function > returned. Eek, have we not SmPL'ify'd a proof yet to ensure code like this no longer exists? Julia? :) > Several commits have been applied to fix those bugs. I actualy found *tons* ! > Finding and backporting them and their dependencies will not be easy. May the SmPL proof be with us. > I suggest this patch not be applied. Thanks for the review Alan! Luis -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
