Re: [Question] SCSI_EH: How does EH guarantee there is no UAF of scsi_cmnd if host reset failed

[Hannes Reinecke <hare@suse.de>]

On 4/19/22 16:28, Wenchao Hao wrote:
> Hi all, I am wondered how does SCSI EH guarantee there is no UAF of scsi_cmnd
> if host reset failed. If host reset failed and eh_cmd_q of shost is not empty,
> these command in eh_cmd_q would be added to done_q in scsi_eh_offline_sdevs()
> and finished by scsi_eh_flush_done_q(). So these scsi_cmnd and it's related
> request would be freed.
> 
Yes.

> While since host reset failed, we can not guarantee the LLDDs has cleared all
> references to these commands in eh_cmd_q. Is there any possibility that the
> LLDDs reference to these commands? If this happened, then a using after free
> issue would occur.
> 
If host reset has failed there are _no_ assumptions we can make about 
commands, and not even about the PCI device itself.
So in effect, once host_reset failed the system is hosed.

We _might_ be able to resurrect the system by doing PCI EEH, but not 
many systems nor drivers implement that.

Cheers,

Hannes