Re: [PATCH] iommu/s390: Fix memory corruption when using identity domain

[Joerg Roedel <joro@8bytes.org>]

On Wed, Aug 27, 2025 at 05:08:27PM -0400, Matthew Rosato wrote:
> zpci_get_iommu_ctrs() returns counter information to be reported as part
> of device statistics; these counters are stored as part of the s390_domain.
> The problem, however, is that the identity domain is not backed by an
> s390_domain and so the conversion via to_s390_domain() yields a bad address
> that is zero'd initially and read on-demand later via a sysfs read.
> These counters aren't necessary for the identity domain; just return NULL
> in this case.
> 
> This issue was discovered via KASAN with reports that look like:
> BUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device
> when using the identity domain for a device on s390.
> 
> Cc: stable@vger.kernel.org
> Fixes: 64af12c6ec3a ("iommu/s390: implement iommu passthrough via identity domain")
> Reported-by: Cam Miller <cam@linux.ibm.com>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>  drivers/iommu/s390-iommu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Applied for -rc, thanks.