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/arm64/lib/strrchr.S | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 arch/arm64/lib/strrchr.S (limited to 'arch/arm64/lib/strrchr.S') diff --git a/arch/arm64/lib/strrchr.S b/arch/arm64/lib/strrchr.S new file mode 100644 index 000000000..a5123cf0c --- /dev/null +++ b/arch/arm64/lib/strrchr.S @@ -0,0 +1,34 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Based on arch/arm/lib/strrchr.S + * + * Copyright (C) 1995-2000 Russell King + * Copyright (C) 2013 ARM Ltd. + */ + +#include +#include + +/* + * Find the last occurrence of a character in a string. + * + * Parameters: + * x0 - str + * x1 - c + * Returns: + * x0 - address of last occurrence of 'c' or 0 + */ +SYM_FUNC_START(__pi_strrchr) + mov x3, #0 + and w1, w1, #0xff +1: ldrb w2, [x0], #1 + cbz w2, 2f + cmp w2, w1 + b.ne 1b + sub x3, x0, #1 + b 1b +2: mov x0, x3 + ret +SYM_FUNC_END(__pi_strrchr) +SYM_FUNC_ALIAS_WEAK(strrchr, __pi_strrchr) +EXPORT_SYMBOL_NOKASAN(strrchr) -- cgit v1.3.1