From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- include/kvm/iodev.h | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 include/kvm/iodev.h (limited to 'include/kvm/iodev.h') diff --git a/include/kvm/iodev.h b/include/kvm/iodev.h new file mode 100644 index 000000000..56619e332 --- /dev/null +++ b/include/kvm/iodev.h @@ -0,0 +1,58 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +#ifndef __KVM_IODEV_H__ +#define __KVM_IODEV_H__ + +#include +#include + +struct kvm_io_device; +struct kvm_vcpu; + +/** + * kvm_io_device_ops are called under kvm slots_lock. + * read and write handlers return 0 if the transaction has been handled, + * or non-zero to have it passed to the next device. + **/ +struct kvm_io_device_ops { + int (*read)(struct kvm_vcpu *vcpu, + struct kvm_io_device *this, + gpa_t addr, + int len, + void *val); + int (*write)(struct kvm_vcpu *vcpu, + struct kvm_io_device *this, + gpa_t addr, + int len, + const void *val); + void (*destructor)(struct kvm_io_device *this); +}; + + +struct kvm_io_device { + const struct kvm_io_device_ops *ops; +}; + +static inline void kvm_iodevice_init(struct kvm_io_device *dev, + const struct kvm_io_device_ops *ops) +{ + dev->ops = ops; +} + +static inline int kvm_iodevice_read(struct kvm_vcpu *vcpu, + struct kvm_io_device *dev, gpa_t addr, + int l, void *v) +{ + return dev->ops->read ? dev->ops->read(vcpu, dev, addr, l, v) + : -EOPNOTSUPP; +} + +static inline int kvm_iodevice_write(struct kvm_vcpu *vcpu, + struct kvm_io_device *dev, gpa_t addr, + int l, const void *v) +{ + return dev->ops->write ? dev->ops->write(vcpu, dev, addr, l, v) + : -EOPNOTSUPP; +} + +#endif /* __KVM_IODEV_H__ */ -- cgit v1.3.1