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

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Message-ID: <aLrclKHjVgTrNWA_@8bytes.org>
Date: Fri, 5 Sep 2025 14:50:28 +0200
From: Joerg Roedel <joro@...tes.org>
To: Matthew Rosato <mjrosato@...ux.ibm.com>
Cc: schnelle@...ux.ibm.com, will@...nel.org, robin.murphy@....com,
	gerald.schaefer@...ux.ibm.com, jgg@...pe.ca, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	stable@...r.kernel.org, Cam Miller <cam@...ux.ibm.com>
Subject: Re: [PATCH] iommu/s390: Fix memory corruption when using identity
 domain

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@...r.kernel.org
> Fixes: 64af12c6ec3a ("iommu/s390: implement iommu passthrough via identity domain")
> Reported-by: Cam Miller <cam@...ux.ibm.com>
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
>  drivers/iommu/s390-iommu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Applied for -rc, thanks.