linux-kernel - Re: [PATCH v4 rc] iommu: Skip PASID validation for devices without PASID capability

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ae0c9a42-5898-4bc6-b104-aab90ddbc751@amd.com>
Date: Tue, 20 May 2025 14:23:31 +0530
From: Vasant Hegde <vasant.hegde@....com>
To: Tushar Dave <tdave@...dia.com>, joro@...tes.org, will@...nel.org,
 robin.murphy@....com, kevin.tian@...el.com, jgg@...dia.com,
 yi.l.liu@...el.com, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc: linux-pci@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v4 rc] iommu: Skip PASID validation for devices without
 PASID capability

On 5/20/2025 6:49 AM, Tushar Dave wrote:
> Generally PASID support requires ACS settings that usually create
> single device groups, but there are some niche cases where we can get
> multi-device groups and still have working PASID support. The primary
> issue is that PCI switches are not required to treat PASID tagged TLPs
> specially so appropriate ACS settings are required to route all TLPs to
> the host bridge if PASID is going to work properly.
> 
> pci_enable_pasid() does check that each device that will use PASID has
> the proper ACS settings to achieve this routing.
> 
> However, no-PASID devices can be combined with PASID capable devices
> within the same topology using non-uniform ACS settings. In this case
> the no-PASID devices may not have strict route to host ACS flags and
> end up being grouped with the PASID devices.
> 
> This configuration fails to allow use of the PASID within the iommu
> core code which wrongly checks if the no-PASID device supports PASID.
> 
> Fix this by ignoring no-PASID devices during the PASID validation. They
> will never issue a PASID TLP anyhow so they can be ignored.
> 
> Fixes: c404f55c26fc ("iommu: Validate the PASID in iommu_attach_device_pasid()")
> Cc: stable@...r.kernel.org
> Signed-off-by: Tushar Dave <tdave@...dia.com>

Reviewed-by: Vasant Hegde <vasant.hegde@....com>

-Vasant