Messages in this thread | | | Date | Wed, 1 Mar 2023 11:46:31 -0800 | Subject | Re: [PATCH-next] scsi: fix use-after-free problem in scsi_remove_target | From | Bart Van Assche <> |
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On 2/12/23 19:43, Zhong Jinghua wrote: > T0 T1 > sdev_store_delete > scsi_remove_device > device_remove_file > __scsi_remove_device > __iscsi_unbind_session > scsi_remove_target > spin_lock_irqsave > list_for_each_entry > scsi_target_reap // starget->reaf 1 -> 0
What is "reaf"? Did you perhaps want to write "reap_ref"?
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c > index e7893835b99a..0ad357ff4c59 100644 > --- a/drivers/scsi/scsi_sysfs.c > +++ b/drivers/scsi/scsi_sysfs.c > @@ -1561,7 +1561,17 @@ void scsi_remove_target(struct device *dev) > starget->state == STARGET_CREATED_REMOVE) > continue; > if (starget->dev.parent == dev || &starget->dev == dev) { > - kref_get(&starget->reap_ref); > + > + /* > + * If starget->reap_ref is reduced to 0, it means > + * that other processes are releasing it and > + * there is no need to delete it again > + */ > + if (!kref_get_unless_zero(&starget->reap_ref)) { > + spin_unlock_irqrestore(shost->host_lock, flags); > + goto restart; > + } > + > if (starget->state == STARGET_CREATED) > starget->state = STARGET_CREATED_REMOVE; > else
The above comment should be made more clear, e.g. as follows: "If the reference count is already zero, skip this target. Calling kref_get_unless_zero() if the reference count is zero is safe because scsi_target_destroy() will wait until the host lock has been released before freeing starget."
Otherwise this patch looks fine to me.
Thanks,
Bart.
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