Fuzzer reports a KASAN use-after-free bug triggered by a race between KVM_HAS_DEVICE_ATTR and KVM_SET_DEVICE_ATTR ioctls on the AIA device. The root cause is that aia_has_attr() invokes kvm_riscv_aia_aplic_has_attr() without holding dev->kvm->lock, while a concurrent aia_set_attr() may call aia_init() under that lock. When aia_init() fails after kvm_riscv_aia_aplic_init() has succeeded, it calls kvm_riscv_aia_aplic_cleanup() in its fail_cleanup_imsics path, which frees both aplic_state and aplic_state->irqs. The concurrent has_attr path can then dereference the freed aplic->irqs in aplic_read_pending(): irqd = &aplic->irqs[irq]; /* UAF here */ KASAN report: BUG: KASAN: slab-use-after-free in aplic_read_pending arch/riscv/kvm/aia_aplic.c:119 [inline] BUG: KASAN: slab-use-after-free in aplic_read_pending_word arch/riscv/kvm/aia_aplic.c:351 [inline] BUG: KASAN: slab-use-after-free in aplic_mmio_read_offset arch/riscv/kvm/aia_aplic.c:406 Read of size 8 at addr ff600000ba965d58 by task 9498 Call Trace: aplic_read_pending arch/riscv/kvm/aia_aplic.c:119 [inline] aplic_read_pending_word arch/riscv/kvm/aia_aplic.c:351 [inline] aplic_mmio_read_offset arch/riscv/kvm/aia_aplic.c:406 kvm_riscv_aia_aplic_has_attr arch/riscv/kvm/aia_aplic.c:566 aia_has_attr arch/riscv/kvm/aia_device.c:469 allocated by task 9473: kvm_riscv_aia_aplic_init arch/riscv/kvm/aia_aplic.c:583 aia_init arch/riscv/kvm/aia_device.c:248 [inline] aia_set_attr arch/riscv/kvm/aia_device.c:334 freed by task 9473: kvm_riscv_aia_aplic_cleanup arch/riscv/kvm/aia_aplic.c:644 aia_init arch/riscv/kvm/aia_device.c:292 [inline] aia_set_attr arch/riscv/kvm/aia_device.c:334 Fix this race by acquiring dev->kvm->lock in aia_has_attr() before calling kvm_riscv_aia_aplic_has_attr(), consistent with the locking pattern used in aia_get_attr() and aia_set_attr(). Fixes: 289a007b98b06d ("RISC-V: KVM: Expose APLIC registers as attributes of AIA irqchip") Signed-off-by: Jiakai Xu Signed-off-by: Jiakai Xu --- V2 -> V3: - Fixed incorrect locking pattern in aia_has_attr(): avoid returning while holding dev->kvm->lock by storing the return value in a local variable, unlocking, and then returning. V1 -> V2: - Fixed the race by adding locking in aia_has_attr() instead of introducing a new validation function, as suggested by Anup Patel. --- arch/riscv/kvm/aia_device.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/riscv/kvm/aia_device.c b/arch/riscv/kvm/aia_device.c index b195a93add1ce..0722cbaed5ec9 100644 --- a/arch/riscv/kvm/aia_device.c +++ b/arch/riscv/kvm/aia_device.c @@ -437,7 +437,7 @@ static int aia_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr) static int aia_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr) { - int nr_vcpus; + int nr_vcpus, r = -ENXIO; switch (attr->group) { case KVM_DEV_RISCV_AIA_GRP_CONFIG: @@ -466,12 +466,15 @@ static int aia_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr) } break; case KVM_DEV_RISCV_AIA_GRP_APLIC: - return kvm_riscv_aia_aplic_has_attr(dev->kvm, attr->attr); + mutex_lock(&dev->kvm->lock); + r = kvm_riscv_aia_aplic_has_attr(dev->kvm, attr->attr); + mutex_unlock(&dev->kvm->lock); + return r; case KVM_DEV_RISCV_AIA_GRP_IMSIC: return kvm_riscv_aia_imsic_has_attr(dev->kvm, attr->attr); } - return -ENXIO; + return r; } struct kvm_device_ops kvm_riscv_aia_device_ops = { -- 2.34.1