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These kfuncs actually wrapps css_task_iter_{start,next, end}. BPF programs can use these kfuncs through bpf_for_each macro for iteration of all tasks under a css. css_task_iter_*() would try to get the global spin-lock *css_set_lock*, so the bpf side has to be careful in where it allows to use this iter. Currently we only allow it in bpf_lsm and bpf iter-s. Signed-off-by: Chuyi Zhou --- kernel/bpf/helpers.c | 3 ++ kernel/bpf/task_iter.c | 53 +++++++++++++++++++ kernel/bpf/verifier.c | 23 ++++++++ .../testing/selftests/bpf/bpf_experimental.h | 7 +++ 4 files changed, 86 insertions(+) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index b0a9834f1051..189d158c9b7f 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2504,6 +2504,9 @@ BTF_ID_FLAGS(func, bpf_dynptr_slice_rdwr, KF_RET_NULL) BTF_ID_FLAGS(func, bpf_iter_num_new, KF_ITER_NEW) BTF_ID_FLAGS(func, bpf_iter_num_next, KF_ITER_NEXT | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY) +BTF_ID_FLAGS(func, bpf_iter_css_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_iter_css_task_next, KF_ITER_NEXT | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY) BTF_ID_FLAGS(func, bpf_dynptr_adjust) BTF_ID_FLAGS(func, bpf_dynptr_is_null) BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly) diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 7473068ed313..2cfcb4dd8a37 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include "mmap_unlock_work.h" @@ -803,6 +804,58 @@ const struct bpf_func_proto bpf_find_vma_proto = { .arg5_type = ARG_ANYTHING, }; +struct bpf_iter_css_task { + __u64 __opaque[1]; +} __attribute__((aligned(8))); + +struct bpf_iter_css_task_kern { + struct css_task_iter *css_it; +} __attribute__((aligned(8))); + +__bpf_kfunc int bpf_iter_css_task_new(struct bpf_iter_css_task *it, + struct cgroup_subsys_state *css, unsigned int flags) +{ + struct bpf_iter_css_task_kern *kit = (void *)it; + + BUILD_BUG_ON(sizeof(struct bpf_iter_css_task_kern) != sizeof(struct bpf_iter_css_task)); + BUILD_BUG_ON(__alignof__(struct bpf_iter_css_task_kern) != + __alignof__(struct bpf_iter_css_task)); + kit->css_it = NULL; + switch (flags) { + case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED: + case CSS_TASK_ITER_PROCS: + case 0: + break; + default: + return -EINVAL; + } + + kit->css_it = bpf_mem_alloc(&bpf_global_ma, sizeof(struct css_task_iter)); + if (!kit->css_it) + return -ENOMEM; + css_task_iter_start(css, flags, kit->css_it); + return 0; +} + +__bpf_kfunc struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it) +{ + struct bpf_iter_css_task_kern *kit = (void *)it; + + if (!kit->css_it) + return NULL; + return css_task_iter_next(kit->css_it); +} + +__bpf_kfunc void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it) +{ + struct bpf_iter_css_task_kern *kit = (void *)it; + + if (!kit->css_it) + return; + css_task_iter_end(kit->css_it); + bpf_mem_free(&bpf_global_ma, kit->css_it); +} + DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work); static void do_mmap_read_unlock(struct irq_work *entry) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index dbba2b806017..2367483bf4c2 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10332,6 +10332,7 @@ enum special_kfunc_type { KF_bpf_dynptr_clone, KF_bpf_percpu_obj_new_impl, KF_bpf_percpu_obj_drop_impl, + KF_bpf_iter_css_task_new, }; BTF_SET_START(special_kfunc_set) @@ -10354,6 +10355,7 @@ BTF_ID(func, bpf_dynptr_slice_rdwr) BTF_ID(func, bpf_dynptr_clone) BTF_ID(func, bpf_percpu_obj_new_impl) BTF_ID(func, bpf_percpu_obj_drop_impl) +BTF_ID(func, bpf_iter_css_task_new) BTF_SET_END(special_kfunc_set) BTF_ID_LIST(special_kfunc_list) @@ -10378,6 +10380,7 @@ BTF_ID(func, bpf_dynptr_slice_rdwr) BTF_ID(func, bpf_dynptr_clone) BTF_ID(func, bpf_percpu_obj_new_impl) BTF_ID(func, bpf_percpu_obj_drop_impl) +BTF_ID(func, bpf_iter_css_task_new) static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta) { @@ -10902,6 +10905,20 @@ static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env, &meta->arg_rbtree_root.field); } +static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env) +{ + enum bpf_prog_type prog_type = resolve_prog_type(env->prog); + + switch (prog_type) { + case BPF_PROG_TYPE_LSM: + return true; + case BPF_TRACE_ITER: + return env->prog->aux->sleepable; + default: + return false; + } +} + static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta, int insn_idx) { @@ -11152,6 +11169,12 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ break; } case KF_ARG_PTR_TO_ITER: + if (meta->func_id == special_kfunc_list[KF_bpf_iter_css_task_new]) { + if (!check_css_task_iter_allowlist(env)) { + verbose(env, "css_task_iter is only allowed in bpf_lsm and bpf iter-s\n"); + return -EINVAL; + } + } ret = process_iter_arg(env, regno, insn_idx, meta); if (ret < 0) return ret; diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h index 4494eaa9937e..d3ea90f0e142 100644 --- a/tools/testing/selftests/bpf/bpf_experimental.h +++ b/tools/testing/selftests/bpf/bpf_experimental.h @@ -162,4 +162,11 @@ extern void bpf_percpu_obj_drop_impl(void *kptr, void *meta) __ksym; /* Convenience macro to wrap over bpf_obj_drop_impl */ #define bpf_percpu_obj_drop(kptr) bpf_percpu_obj_drop_impl(kptr, NULL) +struct bpf_iter_css_task; +struct cgroup_subsys_state; +extern int bpf_iter_css_task_new(struct bpf_iter_css_task *it, + struct cgroup_subsys_state *css, unsigned int flags) __weak __ksym; +extern struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it) __weak __ksym; +extern void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it) __weak __ksym; + #endif