Commit 79178edd authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by David Gibson
Browse files

vfio/spapr: Fix page size calculation 



Coverity detected an issue (CID 1421903) with potential call of clz64(0)
which returns 64 which make it do "<<" with a negative number.

This checks the mask and avoids undefined behaviour.

In practice pgsizes and memory_region_iommu_get_min_page_size() always
have some common page sizes and even if they did not, the resulting page
size would be 0x8000.0000.0000.0000 (gcc 9.2) and
ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.

Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Message-Id: <20200324063912.25063-1-aik@ozlabs.ru>
Reviewed-by: default avatarGreg Kurz <groug@kaod.org>
Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
parent 3b4f50bd

hw/vfio/spapr.c

+3 −3
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container, 
{

    int ret = 0;

    IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);

    uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);

    uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;

    unsigned entries, bits_total, bits_per_level, max_levels;

    struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };

    long rampagesize = qemu_minrampagesize();
@@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container, 
    if (pagesize > rampagesize) {

        pagesize = rampagesize;

    }

    pagesize = 1ULL << (63 - clz64(container->pgsizes &

                                   (pagesize | (pagesize - 1))));

    pgmask = container->pgsizes & (pagesize | (pagesize - 1));

    pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;

    if (!pagesize) {

        error_report("Host doesn't support page size 0x%"PRIx64

                     ", the supported mask is 0x%lx",