Messages in this thread | | | Date | Mon, 6 Mar 2023 16:29:16 +0800 | Subject | Re: [PATCH-next] scsi: fix use-after-free problem in scsi_remove_target | From | zhongjinghua <> |
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在 2023/3/2 3:46, Bart Van Assche 写道: > 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"? Yes, I will modify late. > >> 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."
Agree. Thanks for your e.g.
I will send the v2 late.
> > Otherwise this patch looks fine to me. > > Thanks, > > Bart. > > Thanks,
Jinghua
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