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/mm/physaddr.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 arch/x86/mm/physaddr.c (limited to 'arch/x86/mm/physaddr.c') diff --git a/arch/x86/mm/physaddr.c b/arch/x86/mm/physaddr.c new file mode 100644 index 000000000..8d31c6b9e --- /dev/null +++ b/arch/x86/mm/physaddr.c @@ -0,0 +1,89 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include + +#include +#include + +#include "physaddr.h" + +#ifdef CONFIG_X86_64 + +#ifdef CONFIG_DEBUG_VIRTUAL +unsigned long __phys_addr(unsigned long x) +{ + unsigned long y = x - __START_KERNEL_map; + + /* use the carry flag to determine if x was < __START_KERNEL_map */ + if (unlikely(x > y)) { + x = y + phys_base; + + VIRTUAL_BUG_ON(y >= KERNEL_IMAGE_SIZE); + } else { + x = y + (__START_KERNEL_map - PAGE_OFFSET); + + /* carry flag will be set if starting x was >= PAGE_OFFSET */ + VIRTUAL_BUG_ON((x > y) || !phys_addr_valid(x)); + } + + return x; +} +EXPORT_SYMBOL(__phys_addr); +#endif + +bool __virt_addr_valid(unsigned long x) +{ + unsigned long y = x - __START_KERNEL_map; + + /* use the carry flag to determine if x was < __START_KERNEL_map */ + if (unlikely(x > y)) { + x = y + phys_base; + + if (y >= KERNEL_IMAGE_SIZE) + return false; + } else { + x = y + (__START_KERNEL_map - PAGE_OFFSET); + + /* carry flag will be set if starting x was >= PAGE_OFFSET */ + if ((x > y) || !phys_addr_valid(x)) + return false; + } + + return pfn_valid(x >> PAGE_SHIFT); +} +EXPORT_SYMBOL(__virt_addr_valid); + +#else + +#ifdef CONFIG_DEBUG_VIRTUAL +unsigned long __phys_addr(unsigned long x) +{ + unsigned long phys_addr = x - PAGE_OFFSET; + /* VMALLOC_* aren't constants */ + VIRTUAL_BUG_ON(x < PAGE_OFFSET); + VIRTUAL_BUG_ON(__vmalloc_start_set && is_vmalloc_addr((void *) x)); + /* max_low_pfn is set early, but not _that_ early */ + if (max_low_pfn) { + VIRTUAL_BUG_ON((phys_addr >> PAGE_SHIFT) > max_low_pfn); + BUG_ON(slow_virt_to_phys((void *)x) != phys_addr); + } + return phys_addr; +} +EXPORT_SYMBOL(__phys_addr); +#endif + +bool __virt_addr_valid(unsigned long x) +{ + if (x < PAGE_OFFSET) + return false; + if (__vmalloc_start_set && is_vmalloc_addr((void *) x)) + return false; + if (x >= FIXADDR_START) + return false; + return pfn_valid((x - PAGE_OFFSET) >> PAGE_SHIFT); +} +EXPORT_SYMBOL(__virt_addr_valid); + +#endif /* CONFIG_X86_64 */ -- cgit v1.3.1