On Sat, Sep 28, 2013 at 3:37 PM, Veaceslav Falico <vfalico@xxxxxxxxxx> wrote: > On Thu, Sep 26, 2013 at 11:59:51AM +0200, Veaceslav Falico wrote: >> >> Currently, we first do kobject_put(&entry->kobj) and the kfree(entry), >> however kobject_put() doesn't guarantee us that it was the last reference >> and that the kobj isn't used currently by someone else, so after we >> kfree(entry) with the struct kobject - other users will begin using the >> freed memory, instead of the actual kobject. > > > Hi Bjorn, > > I've seen that you've dropped this bugfix (and the 3 cleanup patches) with > "Changes Requested", however I don't recall any request to change this. I talked to Greg KH about this recently, and he said he might take a look at doing a more extensive cleanup of populate_msi_sysfs() using attribute groups, so I don't know if you want to wait and see whether he does anything, or go ahead on the path you were on. If you continue, my advice is: - Put all these patches in a single series with a version number (I think the next posting would be v3) to help me keep track of them. - In populate_msi_sysfs(), drop the pci_dev_get() (or explain why it's needed). My reasoning is that the "msi_irqs" kset should already hold a reference on the pdev (acquired in kset_create_and_add() -> kset_register() -> kobject_add_internal()), and each irq entry should hold a reference on the kset (see kobject_add_internal() again), so it is redundant to acquire a reference on the pdev directly. This means dropping the pci_dev_put() in msi_kobj_release(), of course. - Move the kfree(entry) from free_msi_irqs() to msi_kobj_release() (I think one of your patches already did this). - In populate_msi_sysfs(), drop the kobject_del() in the out_unroll loop. I think we would only need that if there were a way to create a new irq entry in "msi_irqs" before the old irq entry was released. But I don't think that's possible. We only create irq entries in populate_msi_sysfs(), which always starts with a fresh, empty "msi_irqs" kset. - In free_msi_irqs(), similarly remove the kobject_del(). - Add a kobject_del() before each kset_unregister(dev->msi_kset) call. This will remove "msi_irqs" from sysfs, so future creates will succeed even if somebody still has the old "msi_irqs" open. - Keep the msi_kset cleanup in populate_msi_sysfs() instead of relying on free_msi_irqs(). I think it's less error prone to keep the creation and error path cleanup in the same function. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
