kvm_smccc_set_filter() only rejects a range if its inclusive end,
base + nr_functions - 1, is below base. That catches an empty range
(nr_functions == 0) at every nonzero base, but at base 0 the end wraps
to U32_MAX and KVM tries to insert [0, U32_MAX], which overlaps the
reserved Arm Architecture Calls ranges. KVM_ARM_VM_SMCCC_FILTER then
returns -EEXIST instead of the -EINVAL that the smccc_filter selftest
expects for an empty range.
Reject a zero function count explicitly.
Tested with a userspace reproducer on an arm64 VHE host under QEMU TCG:
EEXIST before, EINVAL after.
Fixes: 821d935c87bc ("KVM: arm64: Introduce support for userspace SMCCC
filtering")
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <[email protected]>
---
arch/arm64/kvm/hypercalls.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index b11b8821c9fb..dfa25bb6f25d 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -185,7 +185,8 @@ static int kvm_smccc_set_filter(struct kvm *kvm, struct
kvm_smccc_filter __user
start = filter.base;
end = start + filter.nr_functions - 1;
- if (end < start || filter.action >= NR_SMCCC_FILTER_ACTIONS)
+ if (!filter.nr_functions || end < start ||
+ filter.action >= NR_SMCCC_FILTER_ACTIONS)
return -EINVAL;
mutex_lock(&kvm->arch.config_lock);
--
2.39.5 (Apple Git-154)
