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 --- lib/math/int_pow.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 lib/math/int_pow.c (limited to 'lib/math/int_pow.c') diff --git a/lib/math/int_pow.c b/lib/math/int_pow.c new file mode 100644 index 000000000..0cf426e69 --- /dev/null +++ b/lib/math/int_pow.c @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * An integer based power function + * + * Derived from drivers/video/backlight/pwm_bl.c + */ + +#include +#include +#include + +/** + * int_pow - computes the exponentiation of the given base and exponent + * @base: base which will be raised to the given power + * @exp: power to be raised to + * + * Computes: pow(base, exp), i.e. @base raised to the @exp power + */ +u64 int_pow(u64 base, unsigned int exp) +{ + u64 result = 1; + + while (exp) { + if (exp & 1) + result *= base; + exp >>= 1; + base *= base; + } + + return result; +} +EXPORT_SYMBOL_GPL(int_pow); -- cgit v1.3.1