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 --- arch/arm/lib/memchr.S | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) create mode 100644 arch/arm/lib/memchr.S (limited to 'arch/arm/lib/memchr.S') diff --git a/arch/arm/lib/memchr.S b/arch/arm/lib/memchr.S new file mode 100644 index 000000000..95bedafd0 --- /dev/null +++ b/arch/arm/lib/memchr.S @@ -0,0 +1,23 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/memchr.S + * + * Copyright (C) 1995-2000 Russell King + * + * ASM optimised string functions + */ +#include +#include + + .text + .align 5 +ENTRY(memchr) +1: subs r2, r2, #1 + bmi 2f + ldrb r3, [r0], #1 + teq r3, r1 + bne 1b + sub r0, r0, #1 +2: movne r0, #0 + ret lr +ENDPROC(memchr) -- cgit v1.3.1