lkml.org 
[lkml]   [2023]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] drivers core: lookup sysfs power group before removal
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.

\
 
 \ /
  Last update: 2023-11-20 13:48    [W:0.150 / U:0.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site