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 --- drivers/iommu/io-pgtable.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 97 insertions(+) create mode 100644 drivers/iommu/io-pgtable.c (limited to 'drivers/iommu/io-pgtable.c') diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c new file mode 100644 index 000000000..843fec8e8 --- /dev/null +++ b/drivers/iommu/io-pgtable.c @@ -0,0 +1,97 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Generic page table allocator for IOMMUs. + * + * Copyright (C) 2014 ARM Limited + * + * Author: Will Deacon + */ + +#include +#include +#include +#include + +static const struct io_pgtable_init_fns * +io_pgtable_init_table[IO_PGTABLE_NUM_FMTS] = { +#ifdef CONFIG_IOMMU_IO_PGTABLE_LPAE + [ARM_32_LPAE_S1] = &io_pgtable_arm_32_lpae_s1_init_fns, + [ARM_32_LPAE_S2] = &io_pgtable_arm_32_lpae_s2_init_fns, + [ARM_64_LPAE_S1] = &io_pgtable_arm_64_lpae_s1_init_fns, + [ARM_64_LPAE_S2] = &io_pgtable_arm_64_lpae_s2_init_fns, + [ARM_MALI_LPAE] = &io_pgtable_arm_mali_lpae_init_fns, +#endif +#ifdef CONFIG_IOMMU_IO_PGTABLE_DART + [APPLE_DART] = &io_pgtable_apple_dart_init_fns, + [APPLE_DART2] = &io_pgtable_apple_dart_init_fns, +#endif +#ifdef CONFIG_IOMMU_IO_PGTABLE_ARMV7S + [ARM_V7S] = &io_pgtable_arm_v7s_init_fns, +#endif +}; + +static int check_custom_allocator(enum io_pgtable_fmt fmt, + struct io_pgtable_cfg *cfg) +{ + /* No custom allocator, no need to check the format. */ + if (!cfg->alloc && !cfg->free) + return 0; + + /* When passing a custom allocator, both the alloc and free + * functions should be provided. + */ + if (!cfg->alloc || !cfg->free) + return -EINVAL; + + /* Make sure the format supports custom allocators. */ + if (io_pgtable_init_table[fmt]->caps & IO_PGTABLE_CAP_CUSTOM_ALLOCATOR) + return 0; + + return -EINVAL; +} + +struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt, + struct io_pgtable_cfg *cfg, + void *cookie) +{ + struct io_pgtable *iop; + const struct io_pgtable_init_fns *fns; + + if (fmt >= IO_PGTABLE_NUM_FMTS) + return NULL; + + if (check_custom_allocator(fmt, cfg)) + return NULL; + + fns = io_pgtable_init_table[fmt]; + if (!fns) + return NULL; + + iop = fns->alloc(cfg, cookie); + if (!iop) + return NULL; + + iop->fmt = fmt; + iop->cookie = cookie; + iop->cfg = *cfg; + + return &iop->ops; +} +EXPORT_SYMBOL_GPL(alloc_io_pgtable_ops); + +/* + * It is the IOMMU driver's responsibility to ensure that the page table + * is no longer accessible to the walker by this point. + */ +void free_io_pgtable_ops(struct io_pgtable_ops *ops) +{ + struct io_pgtable *iop; + + if (!ops) + return; + + iop = io_pgtable_ops_to_pgtable(ops); + io_pgtable_tlb_flush_all(iop); + io_pgtable_init_table[iop->fmt]->free(iop); +} +EXPORT_SYMBOL_GPL(free_io_pgtable_ops); -- cgit v1.3.1