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/vdso/page.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 include/vdso/page.h (limited to 'include/vdso/page.h') diff --git a/include/vdso/page.h b/include/vdso/page.h new file mode 100644 index 000000000..bc47186c0 --- /dev/null +++ b/include/vdso/page.h @@ -0,0 +1,31 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __VDSO_PAGE_H +#define __VDSO_PAGE_H + +#include + +/* + * PAGE_SHIFT determines the page size. + * + * Note: This definition is required because PAGE_SHIFT is used + * in several places throughout the codebase. + */ +#define PAGE_SHIFT CONFIG_PAGE_SHIFT + +#define PAGE_SIZE (_AC(1,UL) << CONFIG_PAGE_SHIFT) + +#if !defined(CONFIG_64BIT) +/* + * Applies only to 32-bit architectures. + * + * Subtle: (1 << CONFIG_PAGE_SHIFT) is an int, not an unsigned long. + * So if we assign PAGE_MASK to a larger type it gets extended the + * way we want (i.e. with 1s in the high bits) while masking a + * 64-bit value such as phys_addr_t. + */ +#define PAGE_MASK (~((1 << CONFIG_PAGE_SHIFT) - 1)) +#else +#define PAGE_MASK (~(PAGE_SIZE - 1)) +#endif + +#endif /* __VDSO_PAGE_H */ -- cgit v1.3.1