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/powerpc/lib/string.S | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 arch/powerpc/lib/string.S (limited to 'arch/powerpc/lib/string.S') diff --git a/arch/powerpc/lib/string.S b/arch/powerpc/lib/string.S new file mode 100644 index 000000000..c3f5e7d31 --- /dev/null +++ b/arch/powerpc/lib/string.S @@ -0,0 +1,43 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * String handling functions for PowerPC. + * + * Copyright (C) 1996 Paul Mackerras. + */ +#include +#include +#include + + .text + +_GLOBAL(strncmp) + PPC_LCMPI 0,r5,0 + beq- 2f + mtctr r5 + addi r5,r3,-1 + addi r4,r4,-1 + .balign IFETCH_ALIGN_BYTES +1: lbzu r3,1(r5) + cmpwi 1,r3,0 + lbzu r0,1(r4) + subf. r3,r0,r3 + beqlr 1 + bdnzt eq,1b + blr +2: li r3,0 + blr +EXPORT_SYMBOL(strncmp) + +_GLOBAL(memchr) + PPC_LCMPI 0,r5,0 + beq- 2f + mtctr r5 + addi r3,r3,-1 + .balign IFETCH_ALIGN_BYTES +1: lbzu r0,1(r3) + cmpw 0,r0,r4 + bdnzf 2,1b + beqlr +2: li r3,0 + blr +EXPORT_SYMBOL(memchr) -- cgit v1.3.1