[PATCH v2] RISC-V: KVM: Fix NULL pointer dereference in SBI v0.1 SEND_IPI handler

The SBI v0.1 SEND_IPI handler iterates over the hart mask and calls
kvm_get_vcpu_by_id() to find the target vcpu for each set bit. When a
guest provides a hart mask containing bits for non-existent vcpu_ids,
kvm_get_vcpu_by_id() returns NULL, which is then unconditionally
dereferenced by kvm_riscv_vcpu_set_interrupt(), causing a kernel crash.

Fix this by adding a NULL check before dereferencing the return value.
If the target vcpu is not found, skip it and continue processing the
remaining valid harts.

Fixes: a046c2d8578c ("RISC-V: KVM: Reorganize SBI code by moving SBI v0.1 to its own file")
Signed-off-by: Jiakai Xu <[email protected]>
Signed-off-by: Jiakai Xu <[email protected]>
Assisted-by: OpenClaw:DeepSeek-V3.2
---
V1 -> V2:
- Changed break to continue when vcpu is not found, as suggested by
  Anup Patel. Non-existent VCPUs in the hart mask should be ignored
  rather than aborting the entire SEND_IPI operation.
---
 arch/riscv/kvm/vcpu_sbi_v01.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_sbi_v01.c b/arch/riscv/kvm/vcpu_sbi_v01.c
index 188d5ea5b3b85..c9c323d4577a9 100644
--- a/arch/riscv/kvm/vcpu_sbi_v01.c
+++ b/arch/riscv/kvm/vcpu_sbi_v01.c
@@ -55,6 +55,8 @@ static int kvm_sbi_ext_v01_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 
 		for_each_set_bit(i, &hmask, BITS_PER_LONG) {
 			rvcpu = kvm_get_vcpu_by_id(vcpu->kvm, i);
+			if (!rvcpu)
+				continue;
 			ret = kvm_riscv_vcpu_set_interrupt(rvcpu, IRQ_VS_SOFT);
 			if (ret < 0)
 				break;
-- 
2.34.1


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