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/memchr.S | 76 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 arch/arm64/lib/memchr.S (limited to 'arch/arm64/lib/memchr.S') diff --git a/arch/arm64/lib/memchr.S b/arch/arm64/lib/memchr.S new file mode 100644 index 000000000..37a9f2a4f --- /dev/null +++ b/arch/arm64/lib/memchr.S @@ -0,0 +1,76 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2021 Arm Ltd. + */ + +#include +#include + +/* + * Find a character in an area of memory. + * + * Parameters: + * x0 - buf + * x1 - c + * x2 - n + * Returns: + * x0 - address of first occurrence of 'c' or 0 + */ + +#define L(label) .L ## label + +#define REP8_01 0x0101010101010101 +#define REP8_7f 0x7f7f7f7f7f7f7f7f + +#define srcin x0 +#define chrin w1 +#define cntin x2 + +#define result x0 + +#define wordcnt x3 +#define rep01 x4 +#define repchr x5 +#define cur_word x6 +#define cur_byte w6 +#define tmp x7 +#define tmp2 x8 + + .p2align 4 + nop +SYM_FUNC_START(__pi_memchr) + and chrin, chrin, #0xff + lsr wordcnt, cntin, #3 + cbz wordcnt, L(byte_loop) + mov rep01, #REP8_01 + mul repchr, x1, rep01 + and cntin, cntin, #7 +L(word_loop): + ldr cur_word, [srcin], #8 + sub wordcnt, wordcnt, #1 + eor cur_word, cur_word, repchr + sub tmp, cur_word, rep01 + orr tmp2, cur_word, #REP8_7f + bics tmp, tmp, tmp2 + b.ne L(found_word) + cbnz wordcnt, L(word_loop) +L(byte_loop): + cbz cntin, L(not_found) + ldrb cur_byte, [srcin], #1 + sub cntin, cntin, #1 + cmp cur_byte, chrin + b.ne L(byte_loop) + sub srcin, srcin, #1 + ret +L(found_word): +CPU_LE( rev tmp, tmp) + clz tmp, tmp + sub tmp, tmp, #64 + add result, srcin, tmp, asr #3 + ret +L(not_found): + mov result, #0 + ret +SYM_FUNC_END(__pi_memchr) +SYM_FUNC_ALIAS_WEAK(memchr, __pi_memchr) +EXPORT_SYMBOL_NOKASAN(memchr) -- cgit v1.3.1