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/x86/lib/misc.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 arch/x86/lib/misc.c (limited to 'arch/x86/lib/misc.c') diff --git a/arch/x86/lib/misc.c b/arch/x86/lib/misc.c new file mode 100644 index 000000000..40b81c338 --- /dev/null +++ b/arch/x86/lib/misc.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 +#include + +/* + * Count the digits of @val including a possible sign. + * + * (Typed on and submitted from hpa's mobile phone.) + */ +int num_digits(int val) +{ + long long m = 10; + int d = 1; + + if (val < 0) { + d++; + val = -val; + } + + while (val >= m) { + m *= 10; + d++; + } + return d; +} -- cgit v1.3.1