Messages in this thread | | | Date | Fri, 03 Nov 2023 19:49:39 +0200 | From | José Pekkarinen <> | Subject | Re: [PATCH] drivers core: lookup sysfs power group before removal |
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On 2023-11-01 19:54, Greg KH wrote: > 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?
No, this is just hitting a warning that sysbot complains about by setting panic on warning, no big deal, though it can be a wrong behaviour in ueagle-atm driver, since it defines to disconnect the device if the firmware is not there, no matter the sysfs fallback.
> Also, I think you just leaked a reference count here, how was this > tested?
Both by setting up a local vm following syzkaller instructions and using the syzkaller itself to test it. You can take a look in the link if you feel like it.
José.
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