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 --- scripts/relocs_check.sh | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) create mode 100755 scripts/relocs_check.sh (limited to 'scripts/relocs_check.sh') diff --git a/scripts/relocs_check.sh b/scripts/relocs_check.sh new file mode 100755 index 000000000..137c66049 --- /dev/null +++ b/scripts/relocs_check.sh @@ -0,0 +1,20 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0-or-later + +# Get a list of all the relocations, remove from it the relocations +# that are known to be legitimate and return this list to arch specific +# script that will look for suspicious relocations. + +objdump="$1" +nm="$2" +vmlinux="$3" + +# Remove from the possible bad relocations those that match an undefined +# weak symbol which will result in an absolute relocation to 0. +# Weak unresolved symbols are of that form in nm output: +# " w _binary__btf_vmlinux_bin_end" +undef_weak_symbols=$($nm "$vmlinux" | awk '$1 ~ /w/ { print $2 }') + +$objdump -R "$vmlinux" | + grep -E '\