From 94c8d1c21be40a845357854f98ec07e21bb14bc9 Mon Sep 17 00:00:00 2001 From: Justin Suess Date: Tue, 9 Jun 2026 22:25:43 +0200 Subject: [PATCH 1/4] bpf: Reject bpf_obj_drop() from tracing progs bpf_obj_drop() runs bpf_obj_free_fields() synchronously for program-allocated objects. When such an object contains NMI unsafe fields, tracing programs that can run from arbitrary instrumented context can reach that destruction from unsafe contexts, including NMI. NMI is likely one instance of this problem, and other instances would include possible unsafe reentrancy. Deferring bpf_obj_drop() is not appealing either: it would add delayed-free machinery to a release operation that otherwise has straightforward synchronous ownership semantics. Reject bpf_obj_drop() and bpf_percpu_obj_drop() from tracing programs that may run from unsafe contexts unless every field in the object's BTF record is explicitly NMI safe. Do not reject sleepable BPF_PROG_TYPE_TRACING programs, since they are not the arbitrary/NMI contexts that motivate the restriction. Note that while bpf_rb_root and bpf_list_head would be NMI safe on their own to free, the objects recursively held by them may not be; be conservative and just mark them as not NMI safe for now. Use a whitelist for the NMI-safe field set instead of listing only known NMI unsafe fields. Locks, async fields, unreferenced kptrs, and refcounts are known to be NMI safe because their destruction is either a no-op, simple state reset, or async cancellation. Referenced kptrs, percpu referenced kptrs, uptrs, graph roots, graph nodes, and any future field type are rejected until audited for arbitrary tracing and NMI contexts. This is less susceptible to future changes in fields that were previously safe by exclusion, and to new fields being added without updating this check. Convert the existing recursive local-object drop success case to a syscall program in the same commit, since this verifier change makes the old tracing program form invalid. The test still exercises bpf_obj_drop() releasing a referenced task kptr from a safe program type. Fixes: ac9f06050a35 ("bpf: Introduce bpf_obj_drop") Signed-off-by: Justin Suess Co-developed-by: Kumar Kartikeya Dwivedi Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260609202548.3571690-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- include/linux/bpf.h | 29 +++++++++++++ kernel/bpf/verifier.c | 17 ++++++++ .../selftests/bpf/prog_tests/task_kfunc.c | 42 ++++++++++++++++++- .../selftests/bpf/progs/task_kfunc_success.c | 13 +++--- 4 files changed, 93 insertions(+), 8 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 62bba7a4876f..0654d2ffadc1 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -492,6 +492,35 @@ static inline bool btf_record_has_field(const struct btf_record *rec, enum btf_f return rec->field_mask & type; } +static inline bool btf_field_is_nmi_safe(enum btf_field_type type) +{ + switch (type) { + case BPF_SPIN_LOCK: + case BPF_RES_SPIN_LOCK: + case BPF_TIMER: + case BPF_WORKQUEUE: + case BPF_TASK_WORK: + case BPF_KPTR_UNREF: + case BPF_REFCOUNT: + return true; + default: + return false; + } +} + +static inline bool btf_record_has_nmi_unsafe_fields(const struct btf_record *rec) +{ + int i; + + if (IS_ERR_OR_NULL(rec)) + return false; + for (i = 0; i < rec->cnt; i++) { + if (!btf_field_is_nmi_safe(rec->fields[i].type)) + return true; + } + return false; +} + static inline void bpf_obj_init(const struct btf_record *rec, void *obj) { int i; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 954b85609f32..eb46a81a8c51 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -205,6 +205,7 @@ static int release_reference_nomark(struct bpf_verifier_state *state, int id); static int release_reference(struct bpf_verifier_env *env, int id); static void invalidate_non_owning_refs(struct bpf_verifier_env *env); static bool in_rbtree_lock_required_cb(struct bpf_verifier_env *env); +static bool is_tracing_prog_type(enum bpf_prog_type type); static int ref_set_non_owning(struct bpf_verifier_env *env, struct bpf_reg_state *reg); static bool is_trusted_reg(struct bpf_verifier_env *env, const struct bpf_reg_state *reg); @@ -12881,6 +12882,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, int *insn_idx_p) { bool sleepable, rcu_lock, rcu_unlock, preempt_disable, preempt_enable; + enum bpf_prog_type prog_type = resolve_prog_type(env->prog); struct bpf_reg_state *regs = cur_regs(env); const char *func_name, *ptr_type_name; const struct btf_type *t, *ptr_type; @@ -12957,6 +12959,21 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, if (err < 0) return err; + if ((is_bpf_obj_drop_kfunc(meta.func_id) || + is_bpf_percpu_obj_drop_kfunc(meta.func_id)) && (is_tracing_prog_type(prog_type) || + /* is_tracing_prog_type() for now doesn't cover non-iterator tracing progs. */ + (prog_type == BPF_PROG_TYPE_TRACING && env->prog->expected_attach_type != BPF_TRACE_ITER + && !env->prog->sleepable))) { + struct btf_struct_meta *struct_meta; + + struct_meta = btf_find_struct_meta(meta.arg_btf, meta.arg_btf_id); + if (struct_meta && btf_record_has_nmi_unsafe_fields(struct_meta->record)) { + verbose(env, "%s cannot be used in tracing programs on types with NMI unsafe fields\n", + func_name); + return -EINVAL; + } + } + if (is_bpf_rbtree_add_kfunc(meta.func_id)) { err = push_callback_call(env, insn, insn_idx, meta.subprogno, set_rbtree_add_callback_state); diff --git a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c index 83b90335967a..e6e95c1416e6 100644 --- a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c +++ b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c @@ -68,6 +68,36 @@ static void run_success_test(const char *prog_name) task_kfunc_success__destroy(skel); } +static void run_syscall_success_test(const char *prog_name) +{ + LIBBPF_OPTS(bpf_test_run_opts, opts); + struct task_kfunc_success *skel; + struct bpf_program *prog; + int err; + + skel = open_load_task_kfunc_skel(); + if (!ASSERT_OK_PTR(skel, "open_load_skel")) + return; + + if (!ASSERT_OK(skel->bss->err, "pre_run_err")) + goto cleanup; + + prog = bpf_object__find_program_by_name(skel->obj, prog_name); + if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name")) + goto cleanup; + + err = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts); + if (!ASSERT_OK(err, "bpf_prog_test_run_opts")) + goto cleanup; + if (!ASSERT_EQ(opts.retval, 0, "retval")) + goto cleanup; + + ASSERT_OK(skel->bss->err, "post_run_err"); + +cleanup: + task_kfunc_success__destroy(skel); +} + static int run_vpid_test(void *prog_name) { struct task_kfunc_success *skel; @@ -140,7 +170,6 @@ static const char * const success_tests[] = { "test_task_acquire_release_argument", "test_task_acquire_release_current", "test_task_acquire_leave_in_map", - "test_task_xchg_release", "test_task_map_acquire_release", "test_task_current_acquire_release", "test_task_from_pid_arg", @@ -151,6 +180,10 @@ static const char * const success_tests[] = { "test_task_kfunc_flavor_relo_not_found", }; +static const char * const syscall_success_tests[] = { + "test_task_xchg_release", +}; + static const char * const vpid_success_tests[] = { "test_task_from_vpid_current", "test_task_from_vpid_invalid", @@ -167,6 +200,13 @@ void test_task_kfunc(void) run_success_test(success_tests[i]); } + for (i = 0; i < ARRAY_SIZE(syscall_success_tests); i++) { + if (!test__start_subtest(syscall_success_tests[i])) + continue; + + run_syscall_success_test(syscall_success_tests[i]); + } + for (i = 0; i < ARRAY_SIZE(vpid_success_tests); i++) { if (!test__start_subtest(vpid_success_tests[i])) continue; diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c index 5fb4fc19d26a..d63a79ee33dc 100644 --- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c +++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c @@ -140,17 +140,17 @@ int BPF_PROG(test_task_acquire_leave_in_map, struct task_struct *task, u64 clone return 0; } -SEC("tp_btf/task_newtask") -int BPF_PROG(test_task_xchg_release, struct task_struct *task, u64 clone_flags) +SEC("syscall") +int test_task_xchg_release(const void *ctx) { - struct task_struct *kptr, *acquired; + struct task_struct *task, *kptr, *acquired; struct __tasks_kfunc_map_value *v, *local; int refcnt, refcnt_after_drop; long status; - if (!is_test_kfunc_task()) - return 0; + (void)ctx; + task = bpf_get_current_task_btf(); status = tasks_kfunc_map_insert(task); if (status) { err = 1; @@ -191,7 +191,7 @@ int BPF_PROG(test_task_xchg_release, struct task_struct *task, u64 clone_flags) return 0; } - /* Stash a copy into local kptr and check if it is released recursively */ + /* Stash a copy into local kptr and check if it is released recursively. */ acquired = bpf_task_acquire(kptr); if (!acquired) { err = 7; @@ -220,7 +220,6 @@ int BPF_PROG(test_task_xchg_release, struct task_struct *task, u64 clone_flags) } bpf_task_release(kptr); - return 0; } From a3a81d247651218e47153f2d2afd7aee236726fd Mon Sep 17 00:00:00 2001 From: Justin Suess Date: Tue, 9 Jun 2026 22:25:44 +0200 Subject: [PATCH 2/4] bpf: Cancel special fields on map value recycle Map update and delete paths currently call bpf_obj_free_fields() when a value is being replaced or recycled. That makes field destruction depend on the context of the update/delete operation. For tracing programs this can include NMI context, where referenced kptr destructors, uptr unpinning, and graph root destruction are not generally safe. Introduce bpf_obj_cancel_fields() for the reusable-value path. It only performs NMI-safe cleanup for timer, workqueue, and task_work fields. Fields that need full destruction are left attached to the recycled value and are destroyed by the final cleanup path instead. Switch array and hashtab update/delete/recycle paths to this cancel helper. Keep bpf_obj_free_fields() for final map destruction and for bpf_mem_alloc destructors. Preallocated hashtabs do not have allocator destructors, so teardown continues to walk the normal and extra elements and fully destroy their fields. This deliberately relaxes the eager-free semantics of map update/delete for special fields. Programs that relied on a recycled map slot becoming empty immediately after update/delete were relying on behavior that cannot be implemented safely from every BPF execution context without offloading arbitrary destructors. There is a chance this change breaks programs making assumptions regarding the eager freeing of fields. If so, we can relax semantics to cancellation only when irqs_disabled() is true in the future. However, theoretically, map values that get reused eagerly already have weaker guarantees as parallel users can recreate freed fields before the new element becomes visible again. Fixes: 14a324f6a67e ("bpf: Wire up freeing of referenced kptr") Signed-off-by: Justin Suess Co-developed-by: Kumar Kartikeya Dwivedi Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260609202548.3571690-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- include/linux/bpf.h | 1 + kernel/bpf/arraymap.c | 8 +-- kernel/bpf/hashtab.c | 32 +++++---- kernel/bpf/syscall.c | 5 ++ .../selftests/bpf/prog_tests/htab_update.c | 4 +- .../selftests/bpf/prog_tests/linked_list.c | 33 ++++----- .../selftests/bpf/prog_tests/map_kptr.c | 10 +-- .../bpf/prog_tests/refcounted_kptr.c | 8 ++- .../testing/selftests/bpf/progs/htab_update.c | 4 +- .../testing/selftests/bpf/progs/linked_list.c | 71 +++++++++++++++++++ .../selftests/bpf/progs/refcounted_kptr.c | 20 +++++- 11 files changed, 146 insertions(+), 50 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 0654d2ffadc1..56f5da2b437f 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2717,6 +2717,7 @@ bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *r void bpf_obj_free_timer(const struct btf_record *rec, void *obj); void bpf_obj_free_workqueue(const struct btf_record *rec, void *obj); void bpf_obj_free_task_work(const struct btf_record *rec, void *obj); +void bpf_obj_cancel_fields(struct bpf_map *map, void *obj); void bpf_obj_free_fields(const struct btf_record *rec, void *obj); void __bpf_obj_drop_impl(void *p, const struct btf_record *rec, bool percpu); diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index e6271a2bf6d6..248b4818178c 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -384,7 +384,7 @@ static long array_map_update_elem(struct bpf_map *map, void *key, void *value, if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY) { val = this_cpu_ptr(array->pptrs[index & array->index_mask]); copy_map_value(map, val, value); - bpf_obj_free_fields(array->map.record, val); + bpf_obj_cancel_fields(map, val); } else { val = array->value + (u64)array->elem_size * (index & array->index_mask); @@ -392,7 +392,7 @@ static long array_map_update_elem(struct bpf_map *map, void *key, void *value, copy_map_value_locked(map, val, value, false); else copy_map_value(map, val, value); - bpf_obj_free_fields(array->map.record, val); + bpf_obj_cancel_fields(map, val); } return 0; } @@ -432,14 +432,14 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value, cpu = map_flags >> 32; ptr = per_cpu_ptr(pptr, cpu); copy_map_value(map, ptr, value); - bpf_obj_free_fields(array->map.record, ptr); + bpf_obj_cancel_fields(map, ptr); goto unlock; } for_each_possible_cpu(cpu) { ptr = per_cpu_ptr(pptr, cpu); val = (map_flags & BPF_F_ALL_CPUS) ? value : value + size * cpu; copy_map_value(map, ptr, val); - bpf_obj_free_fields(array->map.record, ptr); + bpf_obj_cancel_fields(map, ptr); } unlock: rcu_read_unlock(); diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index b4366cad3cfa..9f394e1aa2e8 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -243,6 +243,10 @@ static void htab_free_prealloced_fields(struct bpf_htab *htab) if (IS_ERR_OR_NULL(htab->map.record)) return; + /* + * Preallocated maps do not have a bpf_mem_alloc destructor, so fully + * destroy every element, including the extra elements. + */ if (htab_has_extra_elems(htab)) num_entries += num_possible_cpus(); for (i = 0; i < num_entries; i++) { @@ -833,8 +837,8 @@ static int htab_lru_map_gen_lookup(struct bpf_map *map, return insn - insn_buf; } -static void check_and_free_fields(struct bpf_htab *htab, - struct htab_elem *elem) +static void check_and_cancel_fields(struct bpf_htab *htab, + struct htab_elem *elem) { if (IS_ERR_OR_NULL(htab->map.record)) return; @@ -844,11 +848,11 @@ static void check_and_free_fields(struct bpf_htab *htab, int cpu; for_each_possible_cpu(cpu) - bpf_obj_free_fields(htab->map.record, per_cpu_ptr(pptr, cpu)); + bpf_obj_cancel_fields(&htab->map, per_cpu_ptr(pptr, cpu)); } else { void *map_value = htab_elem_value(elem, htab->map.key_size); - bpf_obj_free_fields(htab->map.record, map_value); + bpf_obj_cancel_fields(&htab->map, map_value); } } @@ -883,7 +887,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node) htab_unlock_bucket(b, flags); if (l == tgt_l) - check_and_free_fields(htab, l); + check_and_cancel_fields(htab, l); return l == tgt_l; } @@ -948,7 +952,7 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key) static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l) { - check_and_free_fields(htab, l); + check_and_cancel_fields(htab, l); if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH) bpf_mem_cache_free(&htab->pcpu_ma, l->ptr_to_pptr); @@ -1001,7 +1005,7 @@ static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l) if (htab_is_prealloc(htab)) { bpf_map_dec_elem_count(&htab->map); - check_and_free_fields(htab, l); + check_and_cancel_fields(htab, l); pcpu_freelist_push(&htab->freelist, &l->fnode); } else { dec_elem_count(htab); @@ -1018,7 +1022,7 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr, /* copy true value_size bytes */ ptr = this_cpu_ptr(pptr); copy_map_value(&htab->map, ptr, value); - bpf_obj_free_fields(htab->map.record, ptr); + bpf_obj_cancel_fields(&htab->map, ptr); } else { u32 size = round_up(htab->map.value_size, 8); void *val; @@ -1028,7 +1032,7 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr, cpu = map_flags >> 32; ptr = per_cpu_ptr(pptr, cpu); copy_map_value(&htab->map, ptr, value); - bpf_obj_free_fields(htab->map.record, ptr); + bpf_obj_cancel_fields(&htab->map, ptr); return; } @@ -1036,7 +1040,7 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr, ptr = per_cpu_ptr(pptr, cpu); val = (map_flags & BPF_F_ALL_CPUS) ? value : value + size * cpu; copy_map_value(&htab->map, ptr, val); - bpf_obj_free_fields(htab->map.record, ptr); + bpf_obj_cancel_fields(&htab->map, ptr); } } } @@ -1252,11 +1256,11 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value, if (l_old) { hlist_nulls_del_rcu(&l_old->hash_node); - /* l_old has already been stashed in htab->extra_elems, free - * its special fields before it is available for reuse. + /* l_old has already been stashed in htab->extra_elems, cancel + * its reusable special fields before it is available for reuse. */ if (htab_is_prealloc(htab)) - check_and_free_fields(htab, l_old); + check_and_cancel_fields(htab, l_old); } htab_unlock_bucket(b, flags); if (l_old && !htab_is_prealloc(htab)) @@ -1269,7 +1273,7 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value, static void htab_lru_push_free(struct bpf_htab *htab, struct htab_elem *elem) { - check_and_free_fields(htab, elem); + check_and_cancel_fields(htab, elem); bpf_map_dec_elem_count(&htab->map); bpf_lru_push_free(&htab->lru, &elem->lru_node); } diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index d4188a992bd8..7ed949f70f82 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -808,6 +808,11 @@ void bpf_obj_free_task_work(const struct btf_record *rec, void *obj) bpf_task_work_cancel_and_free(obj + rec->task_work_off); } +void bpf_obj_cancel_fields(struct bpf_map *map, void *obj) +{ + bpf_map_free_internal_structs(map, obj); +} + void bpf_obj_free_fields(const struct btf_record *rec, void *obj) { const struct btf_field *fields; diff --git a/tools/testing/selftests/bpf/prog_tests/htab_update.c b/tools/testing/selftests/bpf/prog_tests/htab_update.c index ea1a6766fbe9..0a28d4346924 100644 --- a/tools/testing/selftests/bpf/prog_tests/htab_update.c +++ b/tools/testing/selftests/bpf/prog_tests/htab_update.c @@ -23,7 +23,7 @@ static void test_reenter_update(void) if (!ASSERT_OK_PTR(skel, "htab_update__open")) return; - bpf_program__set_autoload(skel->progs.bpf_obj_free_fields, true); + bpf_program__set_autoload(skel->progs.bpf_obj_cancel_fields, true); err = htab_update__load(skel); if (!ASSERT_TRUE(!err, "htab_update__load") || err) goto out; @@ -50,7 +50,7 @@ static void test_reenter_update(void) /* * Second update: replace existing element with same key and trigger * the reentrancy of bpf_map_update_elem(). - * check_and_free_fields() calls bpf_obj_free_fields() on the old + * check_and_cancel_fields() calls bpf_obj_cancel_fields() on the old * value, which is where fentry program runs and performs a nested * bpf_map_update_elem(), triggering -EDEADLK. */ diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c index dbff099860ba..8defea0253ed 100644 --- a/tools/testing/selftests/bpf/prog_tests/linked_list.c +++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c @@ -131,13 +131,14 @@ static void test_linked_list_fail_prog(const char *prog_name, const char *err_ms linked_list_fail__destroy(skel); } -static void clear_fields(struct bpf_map *map) +static void clear_fields(struct bpf_program *prog) { - char buf[24]; - int key = 0; + LIBBPF_OPTS(bpf_test_run_opts, opts); + int ret; - memset(buf, 0xff, sizeof(buf)); - ASSERT_OK(bpf_map__update_elem(map, &key, sizeof(key), buf, sizeof(buf), 0), "check_and_free_fields"); + ret = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts); + ASSERT_OK(ret, "clear_fields"); + ASSERT_OK(opts.retval, "clear_fields retval"); } enum { @@ -170,31 +171,31 @@ static void test_linked_list_success(int mode, bool leave_in_map) ASSERT_OK(ret, "map_list_push_pop"); ASSERT_OK(opts.retval, "map_list_push_pop retval"); if (!leave_in_map) - clear_fields(skel->maps.array_map); + clear_fields(skel->progs.clear_map_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.inner_map_list_push_pop), &opts); ASSERT_OK(ret, "inner_map_list_push_pop"); ASSERT_OK(opts.retval, "inner_map_list_push_pop retval"); if (!leave_in_map) - clear_fields(skel->maps.inner_map); + clear_fields(skel->progs.clear_inner_map_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop), &opts); ASSERT_OK(ret, "global_list_push_pop"); ASSERT_OK(opts.retval, "global_list_push_pop retval"); if (!leave_in_map) - clear_fields(skel->maps.bss_A); + clear_fields(skel->progs.clear_global_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop_nested), &opts); ASSERT_OK(ret, "global_list_push_pop_nested"); ASSERT_OK(opts.retval, "global_list_push_pop_nested retval"); if (!leave_in_map) - clear_fields(skel->maps.bss_A); + clear_fields(skel->progs.clear_global_nested_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_array_push_pop), &opts); ASSERT_OK(ret, "global_list_array_push_pop"); ASSERT_OK(opts.retval, "global_list_array_push_pop retval"); if (!leave_in_map) - clear_fields(skel->maps.bss_A); + clear_fields(skel->progs.clear_global_array_list); if (mode == PUSH_POP) goto end; @@ -204,19 +205,19 @@ static void test_linked_list_success(int mode, bool leave_in_map) ASSERT_OK(ret, "map_list_push_pop_multiple"); ASSERT_OK(opts.retval, "map_list_push_pop_multiple retval"); if (!leave_in_map) - clear_fields(skel->maps.array_map); + clear_fields(skel->progs.clear_map_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.inner_map_list_push_pop_multiple), &opts); ASSERT_OK(ret, "inner_map_list_push_pop_multiple"); ASSERT_OK(opts.retval, "inner_map_list_push_pop_multiple retval"); if (!leave_in_map) - clear_fields(skel->maps.inner_map); + clear_fields(skel->progs.clear_inner_map_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop_multiple), &opts); ASSERT_OK(ret, "global_list_push_pop_multiple"); ASSERT_OK(opts.retval, "global_list_push_pop_multiple retval"); if (!leave_in_map) - clear_fields(skel->maps.bss_A); + clear_fields(skel->progs.clear_global_list); if (mode == PUSH_POP_MULT) goto end; @@ -226,19 +227,19 @@ static void test_linked_list_success(int mode, bool leave_in_map) ASSERT_OK(ret, "map_list_in_list"); ASSERT_OK(opts.retval, "map_list_in_list retval"); if (!leave_in_map) - clear_fields(skel->maps.array_map); + clear_fields(skel->progs.clear_map_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.inner_map_list_in_list), &opts); ASSERT_OK(ret, "inner_map_list_in_list"); ASSERT_OK(opts.retval, "inner_map_list_in_list retval"); if (!leave_in_map) - clear_fields(skel->maps.inner_map); + clear_fields(skel->progs.clear_inner_map_list); ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_in_list), &opts); ASSERT_OK(ret, "global_list_in_list"); ASSERT_OK(opts.retval, "global_list_in_list retval"); if (!leave_in_map) - clear_fields(skel->maps.bss_A); + clear_fields(skel->progs.clear_global_list); end: linked_list__destroy(skel); } diff --git a/tools/testing/selftests/bpf/prog_tests/map_kptr.c b/tools/testing/selftests/bpf/prog_tests/map_kptr.c index 03b46f17cf53..ec6f2f2e8308 100644 --- a/tools/testing/selftests/bpf/prog_tests/map_kptr.c +++ b/tools/testing/selftests/bpf/prog_tests/map_kptr.c @@ -51,7 +51,6 @@ static void test_map_kptr_success(bool test_run) ret = bpf_map__update_elem(skel->maps.array_map, &key, sizeof(key), buf, sizeof(buf), 0); ASSERT_OK(ret, "array_map update"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); @@ -59,49 +58,42 @@ static void test_map_kptr_success(bool test_run) ret = bpf_map__update_elem(skel->maps.pcpu_array_map, &key, sizeof(key), pbuf, cpu * sizeof(buf), 0); ASSERT_OK(ret, "pcpu_array_map update"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); ret = bpf_map__delete_elem(skel->maps.hash_map, &key, sizeof(key), 0); ASSERT_OK(ret, "hash_map delete"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); ret = bpf_map__delete_elem(skel->maps.pcpu_hash_map, &key, sizeof(key), 0); ASSERT_OK(ret, "pcpu_hash_map delete"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); ret = bpf_map__delete_elem(skel->maps.hash_malloc_map, &key, sizeof(key), 0); ASSERT_OK(ret, "hash_malloc_map delete"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); ret = bpf_map__delete_elem(skel->maps.pcpu_hash_malloc_map, &key, sizeof(key), 0); ASSERT_OK(ret, "pcpu_hash_malloc_map delete"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); ret = bpf_map__delete_elem(skel->maps.lru_hash_map, &key, sizeof(key), 0); ASSERT_OK(ret, "lru_hash_map delete"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); ret = bpf_map__delete_elem(skel->maps.lru_pcpu_hash_map, &key, sizeof(key), 0); ASSERT_OK(ret, "lru_pcpu_hash_map delete"); - skel->data->ref--; ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts); ASSERT_OK(ret, "test_map_kptr_ref3 refcount"); ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval"); @@ -175,7 +167,7 @@ void serial_test_map_kptr(void) ASSERT_OK(kern_sync_rcu(), "sync rcu"); wait_for_map_release(); - /* Observe refcount dropping to 1 on synchronous delete elem */ + /* Observe refcount dropping to 1 on map release. */ test_map_kptr_success(true); } diff --git a/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c b/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c index d2c0542716a8..1737eba34323 100644 --- a/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c +++ b/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c @@ -57,6 +57,7 @@ void test_percpu_hash_refcounted_kptr_refcount_leak(void) .data_size_in = sizeof(pkt_v4), .repeat = 1, ); + LIBBPF_OPTS(bpf_test_run_opts, syscall_opts); cpu_nr = libbpf_num_possible_cpus(); if (!ASSERT_GT(cpu_nr, 0, "libbpf_num_possible_cpus")) @@ -87,8 +88,11 @@ void test_percpu_hash_refcounted_kptr_refcount_leak(void) if (!ASSERT_EQ(opts.retval, 2, "opts.retval")) goto out; - err = bpf_map__update_elem(map, &key, sizeof(key), values, values_sz, 0); - if (!ASSERT_OK(err, "bpf_map__update_elem")) + fd = bpf_program__fd(skel->progs.clear_percpu_hash_kptr); + err = bpf_prog_test_run_opts(fd, &syscall_opts); + if (!ASSERT_OK(err, "bpf_prog_test_run_opts")) + goto out; + if (!ASSERT_EQ(syscall_opts.retval, 1, "syscall_opts.retval")) goto out; fd = bpf_program__fd(skel->progs.check_percpu_hash_refcount); diff --git a/tools/testing/selftests/bpf/progs/htab_update.c b/tools/testing/selftests/bpf/progs/htab_update.c index 195d3b2fba00..62c1b1325ec2 100644 --- a/tools/testing/selftests/bpf/progs/htab_update.c +++ b/tools/testing/selftests/bpf/progs/htab_update.c @@ -22,8 +22,8 @@ struct { int pid = 0; int update_err = 0; -SEC("?fentry/bpf_obj_free_fields") -int bpf_obj_free_fields(void *ctx) +SEC("?fentry/bpf_obj_cancel_fields") +int bpf_obj_cancel_fields(void *ctx) { __u32 key = 0; struct val value = { .payload = 1 }; diff --git a/tools/testing/selftests/bpf/progs/linked_list.c b/tools/testing/selftests/bpf/progs/linked_list.c index 421f40835acd..fa97faa5358b 100644 --- a/tools/testing/selftests/bpf/progs/linked_list.c +++ b/tools/testing/selftests/bpf/progs/linked_list.c @@ -290,6 +290,77 @@ int test_list_in_list(struct bpf_spin_lock *lock, struct bpf_list_head *head) return list_in_list(lock, head, true); } +#define MAX_LIST_CLEAR_NODES 256 + +static __always_inline +int clear_list(struct bpf_spin_lock *lock, struct bpf_list_head *head) +{ + struct bpf_list_node *n; + int i; + + for (i = 0; i < MAX_LIST_CLEAR_NODES; i++) { + bpf_spin_lock(lock); + n = bpf_list_pop_front(head); + bpf_spin_unlock(lock); + if (!n) + return 0; + bpf_obj_drop(container_of(n, struct foo, node2)); + } + return 1; +} + +SEC("syscall") +int clear_map_list(void *ctx) +{ + struct map_value *v; + + v = bpf_map_lookup_elem(&array_map, &(int){0}); + if (!v) + return 1; + return clear_list(&v->lock, &v->head); +} + +SEC("syscall") +int clear_inner_map_list(void *ctx) +{ + struct map_value *v; + void *map; + + map = bpf_map_lookup_elem(&map_of_maps, &(int){0}); + if (!map) + return 1; + v = bpf_map_lookup_elem(map, &(int){0}); + if (!v) + return 1; + return clear_list(&v->lock, &v->head); +} + +SEC("syscall") +int clear_global_list(void *ctx) +{ + return clear_list(&glock, &ghead); +} + +SEC("syscall") +int clear_global_nested_list(void *ctx) +{ + return clear_list(&ghead_nested.inner.lock, &ghead_nested.inner.head); +} + +SEC("syscall") +int clear_global_array_list(void *ctx) +{ + int ret; + + ret = clear_list(&glock_c, &ghead_array[0]); + if (ret) + return ret; + ret = clear_list(&glock_c, &ghead_array[1]); + if (ret) + return ret; + return clear_list(&glock_c, &ghead_array_one[0]); +} + SEC("tc") int map_list_push_pop(void *ctx) { diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr.c b/tools/testing/selftests/bpf/progs/refcounted_kptr.c index 13de169ad68f..61906f48025c 100644 --- a/tools/testing/selftests/bpf/progs/refcounted_kptr.c +++ b/tools/testing/selftests/bpf/progs/refcounted_kptr.c @@ -1036,13 +1036,31 @@ int percpu_hash_refcount_leak(void *ctx) struct map_value *v; int key = 0; - v = bpf_map_lookup_elem(&percpu_hash, &key); + v = bpf_map_lookup_percpu_elem(&percpu_hash, &key, 0); if (!v) return 0; return __insert_in_list(&head, &lock, &v->node); } +SEC("syscall") +int clear_percpu_hash_kptr(void *ctx) +{ + struct node_data *n; + struct map_value *v; + int key = 0; + + v = bpf_map_lookup_percpu_elem(&percpu_hash, &key, 0); + if (!v) + return 0; + + n = bpf_kptr_xchg(&v->node, NULL); + if (!n) + return 0; + bpf_obj_drop(n); + return probe_read_refcount(); +} + SEC("tc") int check_percpu_hash_refcount(void *ctx) { From 4b84518137ce841eca2acae83096adb829dad05c Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Tue, 9 Jun 2026 22:25:45 +0200 Subject: [PATCH 3/4] selftests/bpf: Exercise unsafe obj drops from tracing progs Add task_kfunc failure cases for bpf_obj_drop() on local objects with referenced kptr fields from tracing and NMI tracing programs. These programs must be rejected because dropping the object would run full special-field destruction synchronously in an unsafe context. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260609202548.3571690-4-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/progs/task_kfunc_failure.c | 40 +++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c index 8e947d445f8e..8942b5478129 100644 --- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c +++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c @@ -5,6 +5,7 @@ #include #include +#include "../bpf_experimental.h" #include "bpf_misc.h" #include "task_kfunc_common.h" @@ -233,6 +234,45 @@ int BPF_PROG(task_kfunc_release_unacquired, struct task_struct *task, u64 clone_ return 0; } +SEC("tp_btf/task_newtask") +__failure __msg("bpf_obj_drop cannot be used in tracing programs on types with NMI unsafe fields") +int BPF_PROG(task_kfunc_obj_drop_with_kptr, struct task_struct *task, u64 clone_flags) +{ + struct __tasks_kfunc_map_value *local; + + local = bpf_obj_new(typeof(*local)); + if (!local) + return 0; + + bpf_obj_drop(local); + return 0; +} + +SEC("tp_btf/task_newtask") +__failure __msg("bpf_obj_drop cannot be used in tracing programs on types with NMI unsafe fields") +int BPF_PROG(task_kfunc_obj_drop_nmi_with_kptr, struct task_struct *task, + u64 clone_flags) +{ + struct __tasks_kfunc_map_value *local; + struct task_struct *acquired, *old; + + (void)clone_flags; + + local = bpf_obj_new(typeof(*local)); + if (!local) + return 0; + + acquired = bpf_task_acquire(task); + if (acquired) { + old = bpf_kptr_xchg(&local->task, acquired); + if (old) + bpf_task_release(old); + } + + bpf_obj_drop(local); + return 0; +} + SEC("tp_btf/task_newtask") __failure __msg("Possibly NULL pointer passed to trusted R1") int BPF_PROG(task_kfunc_from_pid_no_null_check, struct task_struct *task, u64 clone_flags) From 2e7c6cb4d8437a2fe7cd95aac7ca53d7eb05e9f4 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Tue, 9 Jun 2026 22:25:46 +0200 Subject: [PATCH 4/4] selftests/bpf: Exercise kptr map update lifetime Add focused map_kptr coverage for BPF-side map updates that touch values containing referenced kptrs. The new syscall programs stash the testmod refcounted object in an array map, a preallocated hash map, and a no-prealloc hash map, then update the same map from BPF. The refcount must remain elevated after the update, while the userspace runner destroys the skeleton and reuses the existing refcount wait to confirm map teardown releases the kptr. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260609202548.3571690-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/prog_tests/map_kptr.c | 56 ++++++++++++ tools/testing/selftests/bpf/progs/map_kptr.c | 89 ++++++++++++++++++- 2 files changed, 142 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/map_kptr.c b/tools/testing/selftests/bpf/prog_tests/map_kptr.c index ec6f2f2e8308..17e707dddda8 100644 --- a/tools/testing/selftests/bpf/prog_tests/map_kptr.c +++ b/tools/testing/selftests/bpf/prog_tests/map_kptr.c @@ -143,12 +143,68 @@ static void wait_for_map_release(void) map_kptr__destroy(skel); } +enum map_update_kptr_case { + MAP_UPDATE_KPTR_ARRAY, + MAP_UPDATE_KPTR_HASH, + MAP_UPDATE_KPTR_HASH_MALLOC, +}; + +static struct bpf_program *map_update_kptr_prog(struct map_kptr *skel, + enum map_update_kptr_case test) +{ + switch (test) { + case MAP_UPDATE_KPTR_ARRAY: + return skel->progs.test_array_map_update_kptr; + case MAP_UPDATE_KPTR_HASH: + return skel->progs.test_hash_map_update_kptr; + case MAP_UPDATE_KPTR_HASH_MALLOC: + return skel->progs.test_hash_malloc_map_update_kptr; + } + + return NULL; +} + +static void test_map_update_kptr(enum map_update_kptr_case test) +{ + LIBBPF_OPTS(bpf_test_run_opts, opts); + struct map_kptr *skel; + struct bpf_program *prog; + int ret; + + skel = map_kptr__open_and_load(); + if (!ASSERT_OK_PTR(skel, "map_kptr__open_and_load")) + return; + + prog = map_update_kptr_prog(skel, test); + if (!ASSERT_OK_PTR(prog, "map_update_kptr_prog")) + goto out; + + ret = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts); + if (!ASSERT_OK(ret, "map_update_kptr")) + goto out; + if (!ASSERT_OK(opts.retval, "map_update_kptr retval")) + goto out; + + ASSERT_EQ(skel->bss->num_of_refs, 3, "refs_after_update"); + +out: + map_kptr__destroy(skel); + wait_for_map_release(); +} + void serial_test_map_kptr(void) { struct rcu_tasks_trace_gp *skel; RUN_TESTS(map_kptr_fail); + if (test__start_subtest("update_array_map_kptr")) + test_map_update_kptr(MAP_UPDATE_KPTR_ARRAY); + if (test__start_subtest("update_hash_map_kptr")) + test_map_update_kptr(MAP_UPDATE_KPTR_HASH); + if (test__start_subtest("update_hash_malloc_map_kptr")) + test_map_update_kptr(MAP_UPDATE_KPTR_HASH_MALLOC); + skel = rcu_tasks_trace_gp__open_and_load(); if (!ASSERT_OK_PTR(skel, "rcu_tasks_trace_gp__open_and_load")) return; diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c b/tools/testing/selftests/bpf/progs/map_kptr.c index e708ffbe1f61..3fbefc568e0a 100644 --- a/tools/testing/selftests/bpf/progs/map_kptr.c +++ b/tools/testing/selftests/bpf/progs/map_kptr.c @@ -489,8 +489,7 @@ int test_map_kptr_ref3(struct __sk_buff *ctx) int num_of_refs; -SEC("syscall") -int count_ref(void *ctx) +static __always_inline int read_ref_count(void) { struct prog_test_ref_kfunc *p; unsigned long arg = 0; @@ -500,11 +499,95 @@ int count_ref(void *ctx) return 1; num_of_refs = p->cnt.refs.counter; - bpf_kfunc_call_test_release(p); return 0; } +SEC("syscall") +int count_ref(void *ctx) +{ + return read_ref_count(); +} + +static __always_inline int stash_ref_ptr(struct map_value *v) +{ + struct prog_test_ref_kfunc *p, *old; + unsigned long arg = 0; + + p = bpf_kfunc_call_test_acquire(&arg); + if (!p) + return 1; + + old = bpf_kptr_xchg(&v->ref_ptr, p); + if (old) { + bpf_kfunc_call_test_release(old); + old = bpf_kptr_xchg(&v->ref_ptr, NULL); + if (old) + bpf_kfunc_call_test_release(old); + return 2; + } + return 0; +} + +static __always_inline int check_refs(int expected) +{ + int ret; + + ret = read_ref_count(); + if (ret) + return ret; + return num_of_refs == expected ? 0 : 3; +} + +SEC("syscall") +int test_array_map_update_kptr(void *ctx) +{ + struct map_value init = {}, *v; + int key = 0, ret; + + v = bpf_map_lookup_elem(&array_map, &key); + if (!v) + return 1; + ret = stash_ref_ptr(v); + if (ret) + return ret; + ret = check_refs(3); + if (ret) + return ret; + ret = bpf_map_update_elem(&array_map, &key, &init, BPF_EXIST); + if (ret) + return 4; + return check_refs(3); +} + +#define DEFINE_HASH_UPDATE_KPTR_TEST(name, map) \ +SEC("syscall") \ +int name(void *ctx) \ +{ \ + struct map_value init = {}, *v; \ + int key = 0, ret; \ + \ + ret = bpf_map_update_elem(&map, &key, &init, BPF_NOEXIST); \ + if (ret) \ + return 1; \ + v = bpf_map_lookup_elem(&map, &key); \ + if (!v) \ + return 2; \ + ret = stash_ref_ptr(v); \ + if (ret) \ + return ret; \ + ret = check_refs(3); \ + if (ret) \ + return ret; \ + ret = bpf_map_update_elem(&map, &key, &init, BPF_EXIST); \ + if (ret) \ + return 4; \ + return check_refs(3); \ +} + +DEFINE_HASH_UPDATE_KPTR_TEST(test_hash_map_update_kptr, hash_map) +DEFINE_HASH_UPDATE_KPTR_TEST(test_hash_malloc_map_update_kptr, hash_malloc_map) + SEC("syscall") int test_ls_map_kptr_ref1(void *ctx) {