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 --- tools/virtio/asm/barrier.h | 32 ++++++++++++++++++++++++++++++++ tools/virtio/asm/percpu_types.h | 7 +++++++ 2 files changed, 39 insertions(+) create mode 100644 tools/virtio/asm/barrier.h create mode 100644 tools/virtio/asm/percpu_types.h (limited to 'tools/virtio/asm') diff --git a/tools/virtio/asm/barrier.h b/tools/virtio/asm/barrier.h new file mode 100644 index 000000000..468435ed6 --- /dev/null +++ b/tools/virtio/asm/barrier.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include +#if defined(__i386__) || defined(__x86_64__) +#define barrier() asm volatile("" ::: "memory") +#define virt_mb() __sync_synchronize() +#define virt_rmb() barrier() +#define virt_wmb() barrier() +/* Atomic store should be enough, but gcc generates worse code in that case. */ +#define virt_store_mb(var, value) do { \ + typeof(var) virt_store_mb_value = (value); \ + __atomic_exchange(&(var), &virt_store_mb_value, &virt_store_mb_value, \ + __ATOMIC_SEQ_CST); \ + barrier(); \ +} while (0); +/* Weak barriers should be used. If not - it's a bug */ +# define mb() abort() +# define dma_rmb() abort() +# define dma_wmb() abort() +#elif defined(__aarch64__) +#define dmb(opt) asm volatile("dmb " #opt : : : "memory") +#define virt_mb() __sync_synchronize() +#define virt_rmb() dmb(ishld) +#define virt_wmb() dmb(ishst) +#define virt_store_mb(var, value) do { WRITE_ONCE(var, value); dmb(ish); } while (0) +/* Weak barriers should be used. If not - it's a bug */ +# define mb() abort() +# define dma_rmb() abort() +# define dma_wmb() abort() +#else +#error Please fill in barrier macros +#endif + diff --git a/tools/virtio/asm/percpu_types.h b/tools/virtio/asm/percpu_types.h new file mode 100644 index 000000000..4eb53d93c --- /dev/null +++ b/tools/virtio/asm/percpu_types.h @@ -0,0 +1,7 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_PERCPU_TYPES_H +#define _ASM_PERCPU_TYPES_H + +#define __percpu_qual + +#endif /* _ASM_PERCPU_TYPES_H */ -- cgit v1.3.1