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KVM: arm64: Return -EINVAL for an empty SMCCC filter range at base 0

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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: 821d935c87 ("KVM: arm64: Introduce support for userspace SMCCC filtering")
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260829054856.70549-2-kmehltretter@gmail.com
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Karl Mehltretter 2026-08-29 07:48:55 +02:00 committed by Oliver Upton
parent 4f16c5fc8d
commit 64dc6f1db7
1 changed files with 2 additions and 1 deletions
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3
arch/arm64/kvm/hypercalls.c
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@ -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);