On 8/27/2025 2:08 PM, 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@xxxxxxxxxxxxxxx
Fixes: 64af12c6ec3a ("iommu/s390: implement iommu passthrough via identity domain")
Reported-by: Cam Miller <cam@xxxxxxxxxxxxx>
Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
---
drivers/iommu/s390-iommu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 9c80d61deb2c..d7370347c910 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -1032,7 +1032,8 @@ struct zpci_iommu_ctrs *zpci_get_iommu_ctrs(struct zpci_dev *zdev)
lockdep_assert_held(&zdev->dom_lock);
- if (zdev->s390_domain->type == IOMMU_DOMAIN_BLOCKED)
+ if (zdev->s390_domain->type == IOMMU_DOMAIN_BLOCKED ||
+ zdev->s390_domain->type == IOMMU_DOMAIN_IDENTITY)
return NULL;
s390_domain = to_s390_domain(zdev->s390_domain);
Reviewed-by: Farhan Ali <alifm@xxxxxxxxxxxxx>
