When checking that the storage address of a device entry is valid, it is critical to compute the actual address of the entry, rather than relying on the beginning of the page to match a CPU page of the same size: for example, if the guest places the table at the last 64kB boundary of RAM, but RAM size isn't a multiple of 64kB...
Fix this by computing the actual offset of the device ID in the L2 page, and check the corresponding GFN. Signed-off-by: Marc Zyngier <[email protected]> --- virt/kvm/arm/vgic/vgic-its.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c index 4943d6a..2faf1f4 100644 --- a/virt/kvm/arm/vgic/vgic-its.c +++ b/virt/kvm/arm/vgic/vgic-its.c @@ -727,7 +727,12 @@ static bool vgic_its_check_device_id(struct kvm *kvm, struct vgic_its *its, * Any address beyond our supported 48 bits of PA will be caught * by the actual check in the final step. */ - gfn = (indirect_ptr & GENMASK_ULL(51, 16)) >> PAGE_SHIFT; + indirect_ptr &= GENMASK_ULL(51, 16); + + /* Find the address of the actual entry */ + index = device_id % (SZ_64K / GITS_BASER_ENTRY_SIZE(r)); + indirect_ptr += index * GITS_BASER_ENTRY_SIZE(r); + gfn = indirect_ptr >> PAGE_SHIFT; return kvm_is_visible_gfn(kvm, gfn); } -- 2.1.4 _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
