# git rev-parse -q --verify 7685cf1a7140d1cd184e43c747012fa14cb3dd14^{commit}
7685cf1a7140d1cd184e43c747012fa14cb3dd14
already have revision, skipping fetch
# git checkout -q -f -B kisskb 7685cf1a7140d1cd184e43c747012fa14cb3dd14
# git clean -qxdf
# < git log -1
# commit 7685cf1a7140d1cd184e43c747012fa14cb3dd14
# Author: Alexey Kardashevskiy <aik@ozlabs.ru>
# Date:   Wed Jul 11 21:00:44 2018 +1000
# 
#     KVM: PPC: Check if IOMMU page is contained in the pinned physical page
#     
#     A VM which has:
#      - a DMA capable device passed through to it (eg. network card);
#      - running a malicious kernel that ignores H_PUT_TCE failure;
#      - capability of using IOMMU pages bigger that physical pages
#     can create an IOMMU mapping that exposes (for example) 16MB of
#     the host physical memory to the device when only 64K was allocated to the VM.
#     
#     The remaining 16MB - 64K will be some other content of host memory, possibly
#     including pages of the VM, but also pages of host kernel memory, host
#     programs or other VMs.
#     
#     The attacking VM does not control the location of the page it can map,
#     and is only allowed to map as many pages as it has pages of RAM.
#     
#     We already have a check in drivers/vfio/vfio_iommu_spapr_tce.c that
#     an IOMMU page is contained in the physical page so the PCI hardware won't
#     get access to unassigned host memory; however this check is missing in
#     the KVM fastpath (H_PUT_TCE accelerated code). We were lucky so far and
#     did not hit this yet as the very first time when the mapping happens
#     we do not have tbl::it_userspace allocated yet and fall back to
#     the userspace which in turn calls VFIO IOMMU driver, this fails and
#     the guest does not retry,
#     
#     This stores the smallest preregistered page size in the preregistered
#     region descriptor and changes the mm_iommu_xxx API to check this against
#     the IOMMU page size.
#     
#     This calculates maximum page size as a minimum of the natural region
#     alignment and compound page size. For the page shift this uses the shift
#     returned by find_linux_pte() which indicates how the page is mapped to
#     the current userspace - if the page is huge and this is not a zero, then
#     it is a leaf pte and the page is mapped within the range.
#     
#     Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
#     Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
#     Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/gcc-5.3.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < git log --format=%s --max-count=1 7685cf1a7140d1cd184e43c747012fa14cb3dd14
# < make -s -j 120 ARCH=powerpc O=/kisskb/build/powerpc-fixes_40x_klondike_defconfig_powerpc-5.3 CROSS_COMPILE=/opt/cross/kisskb/gcc-5.3.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  40x/klondike_defconfig
# make -s -j 120 ARCH=powerpc O=/kisskb/build/powerpc-fixes_40x_klondike_defconfig_powerpc-5.3 CROSS_COMPILE=/opt/cross/kisskb/gcc-5.3.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
/kisskb/src/net/Makefile:24: CC cannot link executables. Skipping bpfilter.
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_40x_klondike_defconfig_powerpc-5.3
# Build took: 0:00:13.616414