iommu/s390: Fix memory corruption when using identity domain

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: [email protected]
Fixes: 64af12c6ec3a ("iommu/s390: implement iommu passthrough via identity domain")
Reported-by: Cam Miller <[email protected]>
Signed-off-by: Matthew Rosato <[email protected]>
Tested-by: Cam Miller <[email protected]>
Reviewed-by: Farhan Ali <[email protected]>
Reviewed-by: Niklas Schnelle <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

0 files changed, 0 insertions, 0 deletions