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 --- tools/lib/slab.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 tools/lib/slab.c (limited to 'tools/lib/slab.c') diff --git a/tools/lib/slab.c b/tools/lib/slab.c new file mode 100644 index 000000000..981a21404 --- /dev/null +++ b/tools/lib/slab.c @@ -0,0 +1,54 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include + +#include +#include +#include +#include + +int kmalloc_nr_allocated; +int kmalloc_verbose; + +void *kmalloc(size_t size, gfp_t gfp) +{ + void *ret; + + if (!(gfp & __GFP_DIRECT_RECLAIM)) + return NULL; + + ret = malloc(size); + uatomic_inc(&kmalloc_nr_allocated); + if (kmalloc_verbose) + printf("Allocating %p from malloc\n", ret); + if (gfp & __GFP_ZERO) + memset(ret, 0, size); + return ret; +} + +void kfree(void *p) +{ + if (!p) + return; + uatomic_dec(&kmalloc_nr_allocated); + if (kmalloc_verbose) + printf("Freeing %p to malloc\n", p); + free(p); +} + +void *kmalloc_array(size_t n, size_t size, gfp_t gfp) +{ + void *ret; + + if (!(gfp & __GFP_DIRECT_RECLAIM)) + return NULL; + + ret = calloc(n, size); + uatomic_inc(&kmalloc_nr_allocated); + if (kmalloc_verbose) + printf("Allocating %p from calloc\n", ret); + if (gfp & __GFP_ZERO) + memset(ret, 0, n * size); + return ret; +} -- cgit v1.3.1