Add a null pointer check for imsic_state before dereferencing it in kvm_riscv_aia_imsic_has_attr(). While the function checks that the vcpu exists, it doesn't verify that the vcpu's imsic_state has been initialized, leading to a null pointer dereference when accessed. This issue was discovered during fuzzing of RISC-V KVM code. The crash occurs when userspace calls KVM_HAS_DEVICE_ATTR ioctl on an AIA IMSIC device before the IMSIC state has been fully initialized for a vcpu. The crash manifests as: Unable to handle kernel paging request at virtual address dfffffff00000001 ... epc : kvm_riscv_aia_imsic_has_attr+0x464/0x50e arch/riscv/kvm/aia_imsic.c:998 ... kvm_riscv_aia_imsic_has_attr+0x464/0x50e arch/riscv/kvm/aia_imsic.c:998 aia_has_attr+0x128/0x2bc arch/riscv/kvm/aia_device.c:471 kvm_device_ioctl_attr virt/kvm/kvm_main.c:4722 [inline] kvm_device_ioctl+0x296/0x374 virt/kvm/kvm_main.c:4739 ... The fix adds a check to return -ENODEV if imsic_state is NULL, which is consistent with other error handling in the function and prevents the null pointer dereference. v2: add Fixes tag and drop external link as suggested. Fixes: 5463091a51cf ("RISC-V: KVM: Expose IMSIC registers as attributes of AIA irqchip") Signed-off-by: Jiakai Xu --- arch/riscv/kvm/aia_imsic.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c index e597e86491c3b..9c58a66068447 100644 --- a/arch/riscv/kvm/aia_imsic.c +++ b/arch/riscv/kvm/aia_imsic.c @@ -995,6 +995,9 @@ int kvm_riscv_aia_imsic_has_attr(struct kvm *kvm, unsigned long type) isel = KVM_DEV_RISCV_AIA_IMSIC_GET_ISEL(type); imsic = vcpu->arch.aia_context.imsic_state; + if (!imsic) + return -ENODEV; + return imsic_mrif_isel_check(imsic->nr_eix, isel); } -- 2.34.1