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KVM: arm64: vgic-its: Fix L2 entry validation for indirect tables 

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 <marc.zyngier@arm.com>
This commit is contained in:
Marc Zyngier 2016-07-17 11:48:47 +01:00
parent 333a53ff7f
commit d6c7f865f0
1 changed files with 6 additions and 1 deletions
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7
virt/kvm/arm/vgic/vgic-its.c
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@ -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);
}