From 79178edd2a0b012c5cd27e0168beb83ef4b617ef Mon Sep 17 00:00:00 2001 From: Alexey Kardashevskiy Date: Tue, 24 Mar 2020 17:39:12 +1100 Subject: [PATCH] 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: Alexey Kardashevskiy Message-Id: <20200324063912.25063-1-aik@ozlabs.ru> Reviewed-by: Greg Kurz Signed-off-by: David Gibson --- hw/vfio/spapr.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c index 33692fc86f..2900bd1941 100644 --- a/hw/vfio/spapr.c +++ b/hw/vfio/spapr.c @@ -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",