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/alpha/lib/udelay.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 arch/alpha/lib/udelay.c (limited to 'arch/alpha/lib/udelay.c') diff --git a/arch/alpha/lib/udelay.c b/arch/alpha/lib/udelay.c new file mode 100644 index 000000000..873648263 --- /dev/null +++ b/arch/alpha/lib/udelay.c @@ -0,0 +1,56 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 1993, 2000 Linus Torvalds + * + * Delay routines, using a pre-computed "loops_per_jiffy" value. + */ + +#include +#include /* for udelay's use of smp_processor_id */ +#include +#include +#include + +/* + * Use only for very small delays (< 1 msec). + * + * The active part of our cycle counter is only 32-bits wide, and + * we're treating the difference between two marks as signed. On + * a 1GHz box, that's about 2 seconds. + */ + +void +__delay(int loops) +{ + int tmp; + __asm__ __volatile__( + " rpcc %0\n" + " addl %1,%0,%1\n" + "1: rpcc %0\n" + " subl %1,%0,%0\n" + " bgt %0,1b" + : "=&r" (tmp), "=r" (loops) : "1"(loops)); +} +EXPORT_SYMBOL(__delay); + +#ifdef CONFIG_SMP +#define LPJ cpu_data[smp_processor_id()].loops_per_jiffy +#else +#define LPJ loops_per_jiffy +#endif + +void +udelay(unsigned long usecs) +{ + usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ; + __delay((long)usecs >> 32); +} +EXPORT_SYMBOL(udelay); + +void +ndelay(unsigned long nsecs) +{ + nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ; + __delay((long)nsecs >> 32); +} +EXPORT_SYMBOL(ndelay); -- cgit v1.3.1