From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Xu Yunxiang" <xyx2021@mail.ustc.edu.cn>, <bpf@vger.kernel.org>
Cc: <daniel@iogearbox.net>, <andrii@kernel.org>, <eddyz87@gmail.com>,
<memxor@gmail.com>, <ameryhung@gmail.com>,
<yonghong.song@linux.dev>, <puranjay@kernel.org>
Subject: Re: [PATCH bpf-next v4 1/2] bpf: Track iterator-owned BTF pointer lifetimes
Date: Thu, 17 Sep 2026 14:45:02 +0000 [thread overview]
Message-ID: <DLHO7NCJVWJV.1K8VWK8LFIKGD@gmail.com> (raw)
In-Reply-To: <20260917051948.1588826-2-xyx2021@mail.ustc.edu.cn>
On Thu, Sep 17, 2026 at 01:19 PM Xu Yunxiang <xyx2021@mail.ustc.edu.cn> 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
next prev parent reply other threads:[~2026-09-17 14:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 5:19 [PATCH bpf-next v4 0/2] bpf: Track iterator-owned BTF pointer lifetimes Xu Yunxiang
2026-09-17 5:19 ` [PATCH bpf-next v4 1/2] " Xu Yunxiang
2026-09-17 5:44 ` sashiko-bot
2026-09-17 6:48 ` bot+bpf-ci
2026-09-17 14:45 ` Alexei Starovoitov [this message]
2026-09-17 5:19 ` [PATCH bpf-next v4 2/2] selftests/bpf: Test iterator " Xu Yunxiang
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