Messages in this thread | | | Date | Wed, 1 Nov 2023 18:54:07 +0100 | From | Greg KH <> | Subject | Re: [PATCH] drivers core: lookup sysfs power group before removal |
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On Wed, Nov 01, 2023 at 07:36:27PM +0200, José Pekkarinen wrote: > Hinted by syzboot, there is a few cases where the sysfs power group may > not be there, like the failure while adding it, or adding its runtime > group, or when the sysfs firmware loader fallback fail to populate. In > the last case, the device_del function will be called leading to attempt > to remove the sysfs group. This patch will lookup for it in advance to > grant that it is effectively there before cleaning it up. > > Reported-by: syzbot+95f2e2439b97575ec3c0@syzkaller.appspotmail.com > > Signed-off-by: José Pekkarinen <jose.pekkarinen@foxhound.fi> > --- > drivers/base/power/sysfs.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c > index a1474fb67db9..6601729c4698 100644 > --- a/drivers/base/power/sysfs.c > +++ b/drivers/base/power/sysfs.c > @@ -834,5 +834,7 @@ void dpm_sysfs_remove(struct device *dev) > dev_pm_qos_constraints_destroy(dev); > rpm_sysfs_remove(dev); > sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group); > - sysfs_remove_group(&dev->kobj, &pm_attr_group); > + > + if (kernfs_find_and_get((&dev->kobj)->sd, pm_attr_group.name)) > + sysfs_remove_group(&dev->kobj, &pm_attr_group);
What's to keep it from going away right after finding it?
In other words, what is wrong with removing a group that is not there? What error happens? It should be fine, or are you seeing real code failures somewhere?
Also, I think you just leaked a reference count here, how was this tested?
thanks,
greg k-h
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