From 81f1d7a583fa1fa14f0c4e6140d34b5e3d08d227 Mon Sep 17 00:00:00 2001 From: Benjamin Tissoires Date: Sat, 20 Apr 2024 11:09:13 +0200 Subject: bpf: wq: add bpf_wq_set_callback_impl To support sleepable async callbacks, we need to tell push_async_cb() whether the cb is sleepable or not. The verifier now detects that we are in bpf_wq_set_callback_impl and can allow a sleepable callback to happen. Signed-off-by: Benjamin Tissoires Link: https://lore.kernel.org/r/20240420-bpf_wq-v2-13-6c986a5a741f@kernel.org Signed-off-by: Alexei Starovoitov --- include/linux/bpf_verifier.h | 1 + kernel/bpf/helpers.c | 15 +++++++++++ kernel/bpf/verifier.c | 60 +++++++++++++++++++++++++++++++++++++++----- 3 files changed, 70 insertions(+), 6 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 36d19cd32eb5..9db35530c878 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -426,6 +426,7 @@ struct bpf_verifier_state { * while they are still in use. */ bool used_as_loop_entry; + bool in_sleepable; /* first and last insn idx of this verifier state */ u32 first_insn_idx; diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 1fc002cfe2b1..dd2eaaf77c93 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2711,6 +2711,20 @@ __bpf_kfunc int bpf_wq_init(struct bpf_wq *wq, void *p__map, unsigned int flags) return __bpf_async_init(async, map, flags, BPF_ASYNC_TYPE_WQ); } +__bpf_kfunc int bpf_wq_set_callback_impl(struct bpf_wq *wq, + int (callback_fn)(void *map, int *key, struct bpf_wq *wq), + unsigned int flags, + void *aux__ign) +{ + struct bpf_prog_aux *aux = (struct bpf_prog_aux *)aux__ign; + struct bpf_async_kern *async = (struct bpf_async_kern *)wq; + + if (flags) + return -EINVAL; + + return __bpf_async_set_callback(async, callback_fn, aux, flags, BPF_ASYNC_TYPE_WQ); +} + __bpf_kfunc_end_defs(); BTF_KFUNCS_START(generic_btf_ids) @@ -2789,6 +2803,7 @@ BTF_ID_FLAGS(func, bpf_dynptr_size) BTF_ID_FLAGS(func, bpf_dynptr_clone) BTF_ID_FLAGS(func, bpf_modify_return_test_tp) BTF_ID_FLAGS(func, bpf_wq_init) +BTF_ID_FLAGS(func, bpf_wq_set_callback_impl) BTF_KFUNCS_END(common_btf_ids) static const struct btf_kfunc_id_set common_kfunc_set = { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index cc20fda907fb..9715c88cc025 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -501,8 +501,12 @@ static bool is_dynptr_ref_function(enum bpf_func_id func_id) } static bool is_sync_callback_calling_kfunc(u32 btf_id); +static bool is_async_callback_calling_kfunc(u32 btf_id); +static bool is_callback_calling_kfunc(u32 btf_id); static bool is_bpf_throw_kfunc(struct bpf_insn *insn); +static bool is_bpf_wq_set_callback_impl_kfunc(u32 btf_id); + static bool is_sync_callback_calling_function(enum bpf_func_id func_id) { return func_id == BPF_FUNC_for_each_map_elem || @@ -530,7 +534,8 @@ static bool is_sync_callback_calling_insn(struct bpf_insn *insn) static bool is_async_callback_calling_insn(struct bpf_insn *insn) { - return bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm); + return (bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm)) || + (bpf_pseudo_kfunc_call(insn) && is_async_callback_calling_kfunc(insn->imm)); } static bool is_may_goto_insn(struct bpf_insn *insn) @@ -1429,6 +1434,7 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state, } dst_state->speculative = src->speculative; dst_state->active_rcu_lock = src->active_rcu_lock; + dst_state->in_sleepable = src->in_sleepable; dst_state->curframe = src->curframe; dst_state->active_lock.ptr = src->active_lock.ptr; dst_state->active_lock.id = src->active_lock.id; @@ -2404,7 +2410,7 @@ static void init_func_state(struct bpf_verifier_env *env, /* Similar to push_stack(), but for async callbacks */ static struct bpf_verifier_state *push_async_cb(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx, - int subprog) + int subprog, bool is_sleepable) { struct bpf_verifier_stack_elem *elem; struct bpf_func_state *frame; @@ -2431,6 +2437,7 @@ static struct bpf_verifier_state *push_async_cb(struct bpf_verifier_env *env, * Initialize it similar to do_check_common(). */ elem->st.branches = 1; + elem->st.in_sleepable = is_sleepable; frame = kzalloc(sizeof(*frame), GFP_KERNEL); if (!frame) goto err; @@ -5278,7 +5285,8 @@ bad_type: static bool in_sleepable(struct bpf_verifier_env *env) { - return env->prog->sleepable; + return env->prog->sleepable || + (env->cur_state && env->cur_state->in_sleepable); } /* The non-sleepable programs and sleepable programs with explicit bpf_rcu_read_lock() @@ -9513,7 +9521,7 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins */ env->subprog_info[subprog].is_cb = true; if (bpf_pseudo_kfunc_call(insn) && - !is_sync_callback_calling_kfunc(insn->imm)) { + !is_callback_calling_kfunc(insn->imm)) { verbose(env, "verifier bug: kfunc %s#%d not marked as callback-calling\n", func_id_name(insn->imm), insn->imm); return -EFAULT; @@ -9527,10 +9535,11 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins if (is_async_callback_calling_insn(insn)) { struct bpf_verifier_state *async_cb; - /* there is no real recursion here. timer callbacks are async */ + /* there is no real recursion here. timer and workqueue callbacks are async */ env->subprog_info[subprog].is_async_cb = true; async_cb = push_async_cb(env, env->subprog_info[subprog].start, - insn_idx, subprog); + insn_idx, subprog, + is_bpf_wq_set_callback_impl_kfunc(insn->imm)); if (!async_cb) return -EFAULT; callee = async_cb->frame[0]; @@ -11017,6 +11026,7 @@ enum special_kfunc_type { KF_bpf_percpu_obj_new_impl, KF_bpf_percpu_obj_drop_impl, KF_bpf_throw, + KF_bpf_wq_set_callback_impl, KF_bpf_iter_css_task_new, }; @@ -11041,6 +11051,7 @@ 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_throw) +BTF_ID(func, bpf_wq_set_callback_impl) #ifdef CONFIG_CGROUPS BTF_ID(func, bpf_iter_css_task_new) #endif @@ -11069,6 +11080,7 @@ 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_throw) +BTF_ID(func, bpf_wq_set_callback_impl) #ifdef CONFIG_CGROUPS BTF_ID(func, bpf_iter_css_task_new) #else @@ -11402,12 +11414,28 @@ static bool is_sync_callback_calling_kfunc(u32 btf_id) return btf_id == special_kfunc_list[KF_bpf_rbtree_add_impl]; } +static bool is_async_callback_calling_kfunc(u32 btf_id) +{ + return btf_id == special_kfunc_list[KF_bpf_wq_set_callback_impl]; +} + static bool is_bpf_throw_kfunc(struct bpf_insn *insn) { return bpf_pseudo_kfunc_call(insn) && insn->off == 0 && insn->imm == special_kfunc_list[KF_bpf_throw]; } +static bool is_bpf_wq_set_callback_impl_kfunc(u32 btf_id) +{ + return btf_id == special_kfunc_list[KF_bpf_wq_set_callback_impl]; +} + +static bool is_callback_calling_kfunc(u32 btf_id) +{ + return is_sync_callback_calling_kfunc(btf_id) || + is_async_callback_calling_kfunc(btf_id); +} + static bool is_rbtree_lock_required_kfunc(u32 btf_id) { return is_bpf_rbtree_api_kfunc(btf_id); @@ -12219,6 +12247,16 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, } } + if (is_bpf_wq_set_callback_impl_kfunc(meta.func_id)) { + err = push_callback_call(env, insn, insn_idx, meta.subprogno, + set_timer_callback_state); + if (err) { + verbose(env, "kfunc %s#%d failed callback verification\n", + func_name, meta.func_id); + return err; + } + } + rcu_lock = is_kfunc_bpf_rcu_read_lock(&meta); rcu_unlock = is_kfunc_bpf_rcu_read_unlock(&meta); @@ -16968,6 +17006,9 @@ static bool states_equal(struct bpf_verifier_env *env, if (old->active_rcu_lock != cur->active_rcu_lock) return false; + if (old->in_sleepable != cur->in_sleepable) + return false; + /* for states to be equal callsites have to be the same * and all frame states need to be equivalent */ @@ -19639,6 +19680,13 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, desc->func_id == special_kfunc_list[KF_bpf_rdonly_cast]) { insn_buf[0] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1); *cnt = 1; + } else if (is_bpf_wq_set_callback_impl_kfunc(desc->func_id)) { + struct bpf_insn ld_addrs[2] = { BPF_LD_IMM64(BPF_REG_4, (long)env->prog->aux) }; + + insn_buf[0] = ld_addrs[0]; + insn_buf[1] = ld_addrs[1]; + insn_buf[2] = *insn; + *cnt = 3; } return 0; } -- cgit v1.2.3