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Tue, 21 Oct 2025 13:03:48 -0700 (PDT) Received: from localhost ([2620:10d:c092:500::6:c0ff]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-427f009a75bsm22113354f8f.23.2025.10.21.13.03.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Oct 2025 13:03:48 -0700 (PDT) From: Mykyta Yatsenko To: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com, memxor@gmail.com Cc: Mykyta Yatsenko Subject: [PATCH bpf-next v4 06/10] bpf: add plumbing for file-backed dynptr Date: Tue, 21 Oct 2025 21:03:30 +0100 Message-ID: <20251021200334.220542-7-mykyta.yatsenko5@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251021200334.220542-1-mykyta.yatsenko5@gmail.com> References: <20251021200334.220542-1-mykyta.yatsenko5@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Mykyta Yatsenko Add the necessary verifier plumbing for the new file-backed dynptr type. Introduce two kfuncs for its lifecycle management: * bpf_dynptr_from_file() for initialization * bpf_dynptr_file_discard() for destruction Currently there is no mechanism for kfunc to release dynptr, this patch add one: * Dynptr release function sets meta->release_regno * Call unmark_stack_slots_dynptr() if meta->release_regno is set and dynptr ref_obj_id is set as well. Signed-off-by: Mykyta Yatsenko Acked-by: Eduard Zingerman --- include/linux/bpf.h | 7 ++++++- kernel/bpf/helpers.c | 12 ++++++++++++ kernel/bpf/log.c | 2 ++ kernel/bpf/verifier.c | 31 +++++++++++++++++++++++++------ 4 files changed, 45 insertions(+), 7 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 349bc933fa17..b600230f8b07 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -792,12 +792,15 @@ enum bpf_type_flag { /* DYNPTR points to skb_metadata_end()-skb_metadata_len() */ DYNPTR_TYPE_SKB_META = BIT(19 + BPF_BASE_TYPE_BITS), + /* DYNPTR points to file */ + DYNPTR_TYPE_FILE = BIT(20 + BPF_BASE_TYPE_BITS), + __BPF_TYPE_FLAG_MAX, __BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1, }; #define DYNPTR_TYPE_FLAG_MASK (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | DYNPTR_TYPE_SKB \ - | DYNPTR_TYPE_XDP | DYNPTR_TYPE_SKB_META) + | DYNPTR_TYPE_XDP | DYNPTR_TYPE_SKB_META | DYNPTR_TYPE_FILE) /* Max number of base types. */ #define BPF_BASE_TYPE_LIMIT (1UL << BPF_BASE_TYPE_BITS) @@ -1385,6 +1388,8 @@ enum bpf_dynptr_type { BPF_DYNPTR_TYPE_XDP, /* Points to skb_metadata_end()-skb_metadata_len() */ BPF_DYNPTR_TYPE_SKB_META, + /* Underlying data is a file */ + BPF_DYNPTR_TYPE_FILE, }; int bpf_dynptr_check_size(u64 size); diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index a2ce17ea5edb..bf65b7fb761f 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -4252,6 +4252,16 @@ __bpf_kfunc int bpf_task_work_schedule_resume(struct task_struct *task, struct b return bpf_task_work_schedule(task, tw, map__map, callback, aux__prog, TWA_RESUME); } +__bpf_kfunc int bpf_dynptr_from_file(struct file *file, u32 flags, struct bpf_dynptr *ptr__uninit) +{ + return 0; +} + +__bpf_kfunc int bpf_dynptr_file_discard(struct bpf_dynptr *dynptr) +{ + return 0; +} + __bpf_kfunc_end_defs(); static void bpf_task_work_cancel_scheduled(struct irq_work *irq_work) @@ -4429,6 +4439,8 @@ BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU) BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_dynptr_from_file, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_dynptr_file_discard) BTF_KFUNCS_END(common_btf_ids) static const struct btf_kfunc_id_set common_kfunc_set = { diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c index f50533169cc3..70221aafc35c 100644 --- a/kernel/bpf/log.c +++ b/kernel/bpf/log.c @@ -500,6 +500,8 @@ const char *dynptr_type_str(enum bpf_dynptr_type type) return "xdp"; case BPF_DYNPTR_TYPE_SKB_META: return "skb_meta"; + case BPF_DYNPTR_TYPE_FILE: + return "file"; case BPF_DYNPTR_TYPE_INVALID: return ""; default: diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 157088595788..4c8fd298b99a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -692,6 +692,8 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum bpf_arg_type arg_type) return BPF_DYNPTR_TYPE_XDP; case DYNPTR_TYPE_SKB_META: return BPF_DYNPTR_TYPE_SKB_META; + case DYNPTR_TYPE_FILE: + return BPF_DYNPTR_TYPE_FILE; default: return BPF_DYNPTR_TYPE_INVALID; } @@ -710,6 +712,8 @@ static enum bpf_type_flag get_dynptr_type_flag(enum bpf_dynptr_type type) return DYNPTR_TYPE_XDP; case BPF_DYNPTR_TYPE_SKB_META: return DYNPTR_TYPE_SKB_META; + case BPF_DYNPTR_TYPE_FILE: + return DYNPTR_TYPE_FILE; default: return 0; } @@ -717,7 +721,7 @@ static enum bpf_type_flag get_dynptr_type_flag(enum bpf_dynptr_type type) static bool dynptr_type_refcounted(enum bpf_dynptr_type type) { - return type == BPF_DYNPTR_TYPE_RINGBUF; + return type == BPF_DYNPTR_TYPE_RINGBUF || type == BPF_DYNPTR_TYPE_FILE; } static void __mark_dynptr_reg(struct bpf_reg_state *reg, @@ -12291,6 +12295,8 @@ enum special_kfunc_type { KF_bpf_res_spin_unlock, KF_bpf_res_spin_lock_irqsave, KF_bpf_res_spin_unlock_irqrestore, + KF_bpf_dynptr_from_file, + KF_bpf_dynptr_file_discard, KF___bpf_trap, KF_bpf_task_work_schedule_signal, KF_bpf_task_work_schedule_resume, @@ -12363,6 +12369,8 @@ BTF_ID(func, bpf_res_spin_lock) BTF_ID(func, bpf_res_spin_unlock) BTF_ID(func, bpf_res_spin_lock_irqsave) BTF_ID(func, bpf_res_spin_unlock_irqrestore) +BTF_ID(func, bpf_dynptr_from_file) +BTF_ID(func, bpf_dynptr_file_discard) BTF_ID(func, __bpf_trap) BTF_ID(func, bpf_task_work_schedule_signal) BTF_ID(func, bpf_task_work_schedule_resume) @@ -13326,6 +13334,11 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ dynptr_arg_type |= DYNPTR_TYPE_XDP; } else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb_meta]) { dynptr_arg_type |= DYNPTR_TYPE_SKB_META; + } else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_file]) { + dynptr_arg_type |= DYNPTR_TYPE_FILE; + } else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_file_discard]) { + dynptr_arg_type |= DYNPTR_TYPE_FILE; + meta->release_regno = regno; } else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_clone] && (dynptr_arg_type & MEM_UNINIT)) { enum bpf_dynptr_type parent_type = meta->initialized_dynptr.type; @@ -14006,12 +14019,18 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, * PTR_TO_BTF_ID in bpf_kfunc_arg_meta, do the release now. */ if (meta.release_regno) { - err = release_reference(env, regs[meta.release_regno].ref_obj_id); - if (err) { - verbose(env, "kfunc %s#%d reference has not been acquired before\n", - func_name, meta.func_id); - return err; + struct bpf_reg_state *reg = ®s[meta.release_regno]; + + if (meta.initialized_dynptr.ref_obj_id) { + err = unmark_stack_slots_dynptr(env, reg); + } else { + err = release_reference(env, reg->ref_obj_id); + if (err) + verbose(env, "kfunc %s#%d reference has not been acquired before\n", + func_name, meta.func_id); } + if (err) + return err; } if (meta.func_id == special_kfunc_list[KF_bpf_list_push_front_impl] || -- 2.51.0