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Thu, 17 Sep 2026 07:45:05 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Thu, 17 Sep 2026 14:45:02 +0000 Message-Id: Cc: , , , , , , Subject: Re: [PATCH bpf-next v4 1/2] bpf: Track iterator-owned BTF pointer lifetimes From: "Alexei Starovoitov" To: "Xu Yunxiang" , In-Reply-To: <20260917051948.1588826-2-xyx2021@mail.ustc.edu.cn> References: <20260917051948.1588826-1-xyx2021@mail.ustc.edu.cn> <20260917051948.1588826-2-xyx2021@mail.ustc.edu.cn> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, Sep 17, 2026 at 01:19 PM Xu Yunxiang wrote: > @@ -6219,9 +6231,14 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, > } > > if (atype == BPF_READ && value_regno >= 0) { > + u32 parent_id = reg_lifetime_id(env, reg); > + > ret = mark_btf_ld_reg(env, regs, value_regno, ret, reg->btf, btf_id, flag); > if (ret < 0) > return ret; > + if ((regs[value_regno].type & PTR_TRUSTED) && > + !(regs[value_regno].type & (MEM_RCU | MEM_PERCPU | MEM_USER))) > + regs[value_regno].parent_id = parent_id; > } Any trusted field walked from a referenced pointer now dies with that reference, e.g. file = bpf_get_task_exe_file(task); inode = file->f_inode; bpf_put_file(file); ... inode->i_ino ... loads today and is rejected after this patch, since release_reference() on bpf_put_file() invalidates every reg with parent_id == file's ref id. That's the right thing to do in file case and vma iter case , but likely not the case for many other iters. We need either opt-in or opt-out. Not sure which is better. Certainly some flag. Blank reject for all is probably overkill that might break valid progs. pw-bot: cr