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/arm/lib/delay.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 arch/arm/lib/delay.c (limited to 'arch/arm/lib/delay.c') diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c new file mode 100644 index 000000000..7e9304012 --- /dev/null +++ b/arch/arm/lib/delay.c @@ -0,0 +1,103 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Delay loops based on the OpenRISC implementation. + * + * Copyright (C) 2012 ARM Limited + * + * Author: Will Deacon + */ + +#include +#include +#include +#include +#include + +/* + * Default to the loop-based delay implementation. + */ +struct arm_delay_ops arm_delay_ops __ro_after_init = { + .delay = __loop_delay, + .const_udelay = __loop_const_udelay, + .udelay = __loop_udelay, +}; + +static const struct delay_timer *delay_timer; +static bool delay_calibrated; +static u64 delay_res; + +bool delay_read_timer(unsigned long *timer_val) +{ + if (!delay_timer) + return false; + *timer_val = delay_timer->read_current_timer(); + return true; +} +EXPORT_SYMBOL_GPL(delay_read_timer); + +static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift) +{ + return (cyc * mult) >> shift; +} + +static void __timer_delay(unsigned long cycles) +{ + cycles_t start = get_cycles(); + + while ((get_cycles() - start) < cycles) + cpu_relax(); +} + +static void __timer_const_udelay(unsigned long xloops) +{ + unsigned long long loops = xloops; + loops *= arm_delay_ops.ticks_per_jiffy; + __timer_delay(loops >> UDELAY_SHIFT); +} + +static void __timer_udelay(unsigned long usecs) +{ + __timer_const_udelay(usecs * UDELAY_MULT); +} + +void __init register_current_timer_delay(const struct delay_timer *timer) +{ + u32 new_mult, new_shift; + u64 res; + + clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq, + NSEC_PER_SEC, 3600); + res = cyc_to_ns(1ULL, new_mult, new_shift); + + if (res > 1000) { + pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n", + timer, res); + return; + } + + if (!delay_calibrated && (!delay_res || (res < delay_res))) { + pr_info("Switching to timer-based delay loop, resolution %lluns\n", res); + delay_timer = timer; + lpj_fine = timer->freq / HZ; + delay_res = res; + + /* cpufreq may scale loops_per_jiffy, so keep a private copy */ + arm_delay_ops.ticks_per_jiffy = lpj_fine; + arm_delay_ops.delay = __timer_delay; + arm_delay_ops.const_udelay = __timer_const_udelay; + arm_delay_ops.udelay = __timer_udelay; + } else { + pr_info("Ignoring duplicate/late registration of read_current_timer delay\n"); + } +} + +unsigned long calibrate_delay_is_known(void) +{ + delay_calibrated = true; + return lpj_fine; +} + +void calibration_delay_done(void) +{ + delay_calibrated = true; +} -- cgit v1.3.1